Predicting Boom or Bust for MLB's Most Hyped September Prospect Call-Ups
MLB rewrites its rules for September, allowing teams to roster 40 players instead of the usual 25. This lets squads present prospects with a brief taste of The Show.
Most late arrivals take a minimal peep in scarce playing time, but some additions will run with the opportunity. After a disappointing start banished him back to the minors, Byron Buxton regained his 2017 starting gig with nine homers and a 1.011 OPS following last year's September call-up. Jharel Cotton authored a 2.15 ERA in his first five MLB starts.
Note that these "Boom" or "Bust" assessments only focus on the player's predicted immediate impact. Far too many young talents get prematurely discarded while learning the ropes.
Before freaking out over a slumping rookie, remember that Aaron Judge hit .179 with a 44.2 strikeout percentage in last year's big league introduction.
Also, for anyone wondering how Michael Saunders or Fernando Salas will respond to second chances, only rookies were considered for this list. Most of them are making their MLB debuts, but a few briefly tested the waters earlier this season.
Let's determine which marquee September promotions will turn heads down the stretch.
Honorable Mentions
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RHP Tyler Glasnow, Pittsburgh Pirates
According to Pirates Prospects' Alan Saunders, the Pittsburgh Pirates will let Tyler Glasnow play out the Triple-A postseason before bringing him back to the majors. When he arrives later in the month, the organization will hope to see the 24-year-old's progress continue.
The highly regarded pitching prospect surrendered 53 runs (45 earned) over a dozen messy major league starts this season. He has rebounded in Triple-A with a 1.93 ERA and 140 strikeouts in 93.1 innings, so don't forget about the 6'8" righty just yet.
C Chance Sisco, Baltimore Orioles
Despite arriving on Sept. 1, Chance Sisco has yet to record his first major league plate appearance. Entrenched in a competitive wild-card frenzy, the Baltimore Orioles are unlikely to give significant playing time to a rookie catcher who batted .267/.340/.395 in Triple-A.
MLB.com's No. 49-ranked prospect remains their catcher of the future, which could arrive next year if Welington Castillo signs elsewhere. Although a bat-first talent, the 22-year-old lefty is developing into a solid defender.
He won't receive much work in September, but Sisco should get some playing time in 2018.
OF Teoscar Hernandez, Toronto Blue Jays
Acquired from the Houston Astros for Francisco Liriano, Teoscar Hernandez is getting a September audition for the Toronto Blue Jays. The 24-year-old outfielder is 2-for-13 with a walk through four games.
He continued to display power and speed in the minors with 18 home runs and 16 steals for Houston and Toronto's Triple-A squads. Yet he hit .222 with a steep rise in strikeouts and decline in walks after the late-July trade. Toronto should nevertheless test his talent with no playoff hopes at stake.
RHP Carson Fulmer, Chicago White Sox
Carson Fulmer's 2017 debut didn't go well. Brought in to start on Aug. 21, the 2015 first-round pick surrendered three walks, two home runs and six runs over 1.1 innings. He went back to Triple-A until September, when he returned to pitch in relief.
The 23-year-old righty has since allowed one run in 4.2 frames. Including last year's troublesome start, he has a 9.17 ERA with one more strikeout (13) than walk. He's in danger of losing any buzz as a future starter.
OF Tim Tebow, New York Mets
Sighs. This writer wants to believe Tim Tebow is here as a joke, but the New York Mets are currently performing a live-action remake of The Simpsons' "Homer at the Bat" episode where Mr. Burns' entire team of ringers—except Darryl Strawberry—suffers increasingly improbable misfortunes.
OF Harrison Bader, St. Louis Cardinals
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Prospect Outlook
The St. Louis Cardinals continue to churn out useful players without glossy prospect pedigrees. Harrison Bader, ranked as MLB.com's No. 98 overall prospect, isn't an out-of-nowhere breakout star like Paul DeJong, but it took a while for everyone to take notice.
During the preseason, FanGraphs' Eric Longenhagen attached a limited ceiling to the outfielder.
"Teams either like Bader as a low-end regular in center or as a good fourth outfielder who could put up excellent rate stats if he's consistently put in situations that are advantageous to his skill set," Longenhagen wrote.
Bader wouldn't be the first RedBird to surpass expectations. The 23-year-old solidified his standing as a future big leaguer by hitting .283/.347/.469 with 20 home runs and 15 steals in 123 Triple-A games.
While the 2015 third-round pick has no standout skill, he does everything well enough to flourish as a perennially under-appreciated contributor.
Boom or Bust in September: Boom
Well, this one is easy. Bader has already blasted three home runs in 23 September plate appearances.
He has started and batted No. 1 or 2 in place of the injured Dexter Fowler, so the Cardinals are trusting him with the NL Central and second wild-card spot still in reach. Yet they shouldn't expect this much power throughout September, and the outfield will get awfully crowded if Fowler's hip holds up.
Bader might have to settle for that fourth outfielder role unless he stays red hot, but he should earn some playing time over the underwhelming Stephen Piscotty and Randal Grichuk.
SP Jack Flaherty, St. Louis Cardinals
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Prospect Outlook
Having already received huge sparks from Bader and rookie starter Luke Weaver, the Cardinals had Jack Flaherty make his major league debut last Friday. Although he has allowed 11 hits and six runs over his first two outings, the 21-year-old righty has also registered 10 strikeouts in nine innings.
Flaherty, who compiled 147 strikeouts in 148.2 Double-A and Triple-A innings, should stockpile plenty more throughout his big league career. MLB.com's No. 52 prospect never needed long to conquer the next minor league level. Since arriving as an 18-year-old in 2014, he earned a 2.77 ERA with 2.6 walks per nine innings through St. Louis's farm system.
The 6'4" starter has elevated his peak velocity to the mid-90s while brandishing a plus changeup and slider. Among high school teammates Lucas Giolito and Max Fried, he may now have the best chance of sticking as a front-line starter.
Boom or Bust in September: Bust
Flaherty already missed his opportunity to make a lasting first impression. He started his career against the San Francisco Giants and San Diego Padres, MLB's bottom-two offenses in terms of runs scored.
Like many neophyte hurlers, he struggled with command and didn't get past the fifth inning in either outing. Even if he had succeeded, he'd be in line to lose the newly received rotation spot once Adam Wainwright returns from an injured elbow.
Held back from a big league role he deserved in April, the 24-year-old Weaver was ready to roll when finally given the overdue opportunity. Flaherty, meanwhile, took an express path to the majors, so give him time before he forms a lethal young rotation alongside Weaver, Carlos Martinez and Alex Reyes.
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2B/SS Franklin Barreto, Oakland Athletics
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Prospect Outlook
If Franklin Barreto doesn't pan out, he will forever be known as the main piece in a crushingly light return for Josh Donaldson, who earned AL MVP honors away from the Oakland Athletics. That's a lot of pressure to put on a 21-year-old middle infielder hoping to play better in his second showing.
Initially promoted in late June, he didn't last long after batting 8-for-42 with 18 strikeouts in 11 games. Those whiffs aren't a new problem for Barreto, who accrued a 27.6 strikeout percentage in 111 Triple-A contests.
It didn't stop him from hitting .290 with 15 home runs and stolen bases apiece, but he doesn't have the plate discipline to flourish in the bigs with so many punchouts.
His future position is also in question. Oakland has played him at both second base and shortstop. Marcus Semien is blocking shortstop now, but he probably needs a position change more than Barretto.
Although not a finished product, the 5'10", 190-pound infielder packs a stout average, power and speed punch.
September Boom or Bust: Bust
MLB.com's No. 36 prospect will upgrade Oakland's infield as soon as next season. This month, however, will host more growing pains.
Barreto continues to strike out in spades and has already committed three errors. No 21-year-old rookie should be expected to have a refined bat and glove.
With the 59-80 Athletics one of few American League teams not in playoff contention, this is the time to let him work out those kinks through experience.
He'll likely continue to struggle in September, and that's fine. Barreto has all the tools to succeed once he gains more major league experience.
1B/2B/3B Ryan McMahon, Colorado Rockies
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Prospect Outlook
After spending a week with the Colorado Rockies in August, Ryan McMahon returned once the rosters expanded to 40.
The 22-year-old might have latched onto another team's starting lineup months ago. A year removed from batting .242/.325/.399, he hit .326/.390/.536 in Double-A and .374/.411/.612 in Triple-A's hitter-friendly Pacific Coast League, tallying a combined 20 home runs and 11 steals.
Sharpening his swing, the lefty slashed his strikeout percentage from 30.1 to 17.7. Likely to never play third base for the Rockies, he broadened his horizons to first and second. Minor League Ball's John Sickels credited him with "viable performance at both positions."
Even if his 2017 numbers benefited from a favorable environment, so do the Rockies. If he carries over his contact gains to Coors Field, McMahon should enjoy a long career of spraying hits across the high-altitude park.
September Boom or Bust: Incomplete
This is a tough call. Although he has just two hits in 18 major league plate appearances, he's an improving hitter who calls Coors Field home.
On the other hand, he will struggle to receive playing time despite his versatility. The Rockies, whose wild-card lead has dwindled to two games, have no infield openings.
Perhaps McMahon can replace upcoming free agent Mark Reynolds next season, but he's currently stuck in a holding pattern. It seems unfair to label him a bust since he wouldn't disappoint if given the opportunity, so he gets no grade.
Francisco Mejia, C, Cleveland Indians
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Prospect Outlook
At age 21, Francisco Mejia will bypass Triple-A to play for the streaking Cleveland Indians.
MLB.com's top-ranked catching prospect has the hit tool to emerge as one baseball's most dangerous sluggers behind the plate. After batting .342 with a 50-game hitting streak in Single-A last year, he hit .297 with 14 homers and seven steals in Double-A.
Even if he's never a Gold Glove catcher, Mejia's bat will forgive any shortcomings. His defense needs more time to develop, but he shouldn't require a position change like new teammate Carlos Santana.
Buster Posey is the only starting catcher batting .300 or better this year. The former MVP could have company when the switch-hitting Mejia locks down Cleveland's job.
September Boom or Bust: Bust
Mejia could be an All-Star one day. For now, he's an extra bat off the bench.
Cleveland has yet to start him behind the plate. A neophyte learning the ropes and his pitchers' tendencies for a World Series contender is too big a burden for a September call-up. Although not the biggest offensive contributor, Yan Gomes is a steady hand calling games and framing pitches.
Those demands often delay a catcher's development. Posey batted .118 with no walks or extra-base hits as a September addition in 2009. Others sometimes need years to round into form.
Mejia will instead pop up in seldom designated-hitter duties. With a chance to poach home-field advantage from the Astros, Cleveland can't give him a full baptism by fire.
SS/3B J.P. Crawford, Philadelphia Phillies
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Prospect Outlook
J.P. Crawford's arrival figured to draw much more excitement.
In Baseball America's 2016 preseason prospect rankings, the Philadelphia Phillies shortstop ranked No. 6, three spots ahead of Trea Turner. Expected to join the majors that season, he instead toiled in Double-A and Triple-A with a .250/.349/.339 slash line.
Those slumps carried over into 2017, as he batted .243/.351/.405 for the Triple-A Lehigh Valley IronPigs. But he showed some life by batting .299 (35-for-117) with 19 walks during his final 30 games. He finally displayed some power with a personal-high 15 home runs.
Although his All-Star upside has taken a hit, Crawford's excellent defense and plate discipline cement his floor as a steady big league shortstop.
September Boom or Bust: Bust
Crawford will get a long-awaited opportunity to prove he belongs. Per CSNPhilly.com's Jim Salisbury, Phillies manager Pete Mackanin plans to play the 22-year-old often over the final weeks.
"I won't say every day, but as much as I can," Mackanin said before Crawford's debut on Tuesday. "The whole idea is to get his feet wet up here."
A long adjustment period to minor league pitching doesn't bode well for a September breakout. He also must get situated to third base, even though shortstop remains his long-term position.
Crawford is still a vital part of Philadelphia's future, but don't expect him to hit for much average or pop out of the gate.
OF Alex Verdugo, Los Angeles Dodgers
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Prospect Outlook
On July 27, MLB.com's Mark Feinsand wrote that the Texas Rangers were "enamored with outfielder Alex Verdugo" as a return for Yu Darvish. Over a month later, the Los Angeles Dodgers somehow have both Verdugo and Darvish.
The Dodgers kept their second-best prospect, as ranked by MLB.com. He and pitcher Walker Buehler, the only player placed above the 21-year-old outfielder, both received September call-ups.
Although Verdugo mustered just six home runs in 495 Triple-A plate appearances, he displayed plate presence beyond his years by batting .314 with more walks (52) than strikeouts (50). The former high school pitcher also has an incredible arm and enough range to adequately handle center if Joc Pederson doesn't bounce back.
If the line-drive hitter develops fence-clearing power, he could mature into another homegrown All-Star alongside Corey Seager and Cody Bellinger.
September Boom or Bust: Boom
It's unfair to group the newcomer with Seager—who hit .337/.425/.561 as a 2015 September call-up—and Bellinger, who crushed 11 homers in his first 32 career games before smashing another 13 in June. Los Angeles' newest left-handed hitter doesn't wield the same short-term upside.
Verudgo has traded starts in a crowded outfield that also brought back Andre Ethier and Pederson. While going 2-for-12 with two walks and two singles isn't a cause for concern, it won't separate him from the pack.
Nevertheless, he has an approach necessary to reach base and play serviceable defense when called upon. A double-digit NL West advantage could also lead to more reps during the final week or two, so stay patient and look for Verdugo to produce.
RHP Walker Buehler, Los Angeles Dodgers
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Prospect Outlook
Buehler opened 2017 outside of Baseball America's top-100 rankings. He jumped to No. 17 in its midseason update.
Less than two months after dropping to the Dodgers at pick No. 24 of 2015's draft, the Vanderbilt star underwent Tommy John surgery. Dodgers general manager Farhan Zaidi still expressed optimism about his first-round selection to MLB.com's Ken Gurnick.
"We still think he's one of the top pitching talents in the draft, and we have the luxury of being able to play the long game," Zaidi said. "Even if it puts him a year behind, we feel he can come back and justify where we selected him."
It turns out he didn't need to wait too long. After spending nearly all of 2016 recovering, he promptly rediscovered his sky-high ceiling. Working his way from High-A to Triple-A, he recorded 125 strikeouts in 88.2 innings.
The healthy 23-year-old, who fires heat with a sweeping curveball, will have a promising future as a front-line starter. For now, however, he'll join Los Angeles as a reliever.
September Boom or Bust: Boom
In preparation for his new relief gig, Buehler moved to the Triple-A bullpen in August. He faltered in unaccustomed territory, allowing seven runs in 13.1 innings.
He also collected 19 strikeouts. Use a hard-throwing starter in shortened spurts, and he's going to miss plenty of bats.
Dodgers fans should expect more of the same in his abbreviated introduction. Buehler isn't going to become Kenley Jansen's September setup man, but he'll register some punchouts in the process. Next year he could play a far bigger role in their rotation.
OF Victor Robles, Washington Nationals
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Prospect Outlook
The Washington Nationals surprisingly promoted Victor Robles on Thursday, making the 20-year-old phenom MLB’s youngest player. MLB.com projected a 2018 arrival for its No. 4 prospect, and even that seemed aggressive considering he spent six weeks in Double-A.
Robles has all the makings of a future star. After hitting .324 in 37 Double-A contests, he has a career .304/.395/.470 minor league slash line despite debuting at age 17. He’s still developing home run power, but the five-tool outfielder has already stolen 27 bases this season.
It remains to be seen how much he will actually play this September, but his presence in the nation’s capital is an unexpected treat.
September Boom or Bust: Bust
Of all the highlighted prospects, Robles has the highest ceiling. He brandishes legitimate MVP potential in his prime, but let him legally drink a beer first.
The Nationals could feasibly lose every remaining game this season and still win the National League East, so perhaps they will throw him some playing time. With outfielders Bryce Harper and Adam Eaton sidelined, there’s room to give fans a glimpse of the future while relaxing for the postseason.
But it’s possible they will employ the prized prospect as a glorified pinch runner. Per MLB.com’s Jamal Collier, Nationals manager Dusty Baker said Robles is “here to learn more than here to play.”
Perhaps Robles can follow Rafael Devers’ blueprint to immediate success despite skipping Triple-A, but he’s not likely to receive as many reps from a skipper who typically prefers playing veterans. Consider this September call-up a teaser trailer for his true unveiling next summer.
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