The latest installment of this feature on minor league pitchers includes one of the best relievers in the majors from 2011-2012 on the "cold" side and one of the fastest-rising prospects in the Pittsburgh organization on the "hot" side.
Justin Marks, SP, Kansas City Royals
Season stats: 4.54 ERA, 127 IP, 132 H, 57 BB, 118 K (AAA/AA)
When you think of the Royals rotation of the future, Yordano Ventura and Kyle Zimmer are the prospects that immediately come to mind. And Justin Marks is a guy that probably doesn't come to mind at all.
But with Ervin Santana, Bruce Chen and Luke Hochevar all free agents after the season, the starting pitching depth could take a hit, and Marks, with the way he's been pitching over the past two months, could be adding himself to the mix.
The 25-year-old lefty, after 5.1 scoreless innings in his last outing, has a 2.82 ERA with 23 walks and 63 strikeouts over his last 60.2 innings. His success against left-handed hitters (.196 BAA) suggests a future as a bullpen specialist, although it wouldn't be a surprise to see him get a shot in the rotation before he settles into that role.
Vinnie Pestano, RP, Cleveland Indians
Season stats: 4.66 ERA, 9.2 IP, 12 H, 4 BB, 8 K in 9 appearances (AAA/AA)
Pestano's overall numbers in the majors weren't great this season (4.05 ERA), especially compared to what he did in his first two full seasons with the Tribe (2.45 ERA, 10.3 K/9). But his demotion still came as a bit of surprise since he hadn't allowed a run in his last 4.2 innings.
The 27-year-old continued pitching well with Triple-A Columbus, where he pitched 5.2 scoreless innings in his first five outings. But maybe the frustration of his undeserving stay in the minors is kicking in, because he's allowed five earned runs and 10 hits over his last four innings.
He'll be back in September regardless of how he pitches, but this Triple-A stint isn't likely to sit well, especially because it could push his free agency back one year.
Mike Wright, SP, Baltimore Orioles
Season stats: 3.19 ERA, 135.1 IP, 139 H, 36 BB, 129 K in 24 starts
The Orioles' pitching depth took a hit in 2013 with the loss of Dylan Bundy to Tommy John surgery and the trade of Jake Arrieta to the Cubs. But Wright, the team's third-round pick in 2011, has done everything he can to add himself to the equation with a strong overall performance this season.
After posting a 4.91 ERA in 12 Double-A starts in 2012, the 23-year-old has fared much better in his first full season at the level. The 6'6" right-hander is also getting stronger as the season goes along. In July and August, Wright has a 1.91 ERA with 10 walks and 54 strikeouts in 56.2 innings.
Trevor May, SP, Minnesota Twins
Season stats: 4.75 ERA, 132.2 IP, 139 H, 61 BB, 136 K in 24 starts
When the Twins acquired Trevor May from the Phillies for Ben Revere this past offseason, they added a hard-throwing strikeout pitcher to an organization that was sorely in need of one. But while he remains a very good prospect with a high ceiling, the 23-year-old hasn't made much progress, if any at all, in a repeat of the Double-A Eastern League.
After hitting a rough patch in his past three starts, his numbers are nearly identical to 2012 when he posted a 4.87 ERA in 28 starts for Double-A Reading. Over that stretch, May has allowed 17 earned runs and 26 hits in 14 innings with nine walks and 18 strikeouts.
Tanner Peters, SP, Oakland Athletics
Season stats: 148.1 IP, 150 H, 24 BB, 144 K in 25 starts
Allowing five earned runs and eight hits in 5.1 innings during a pitcher's last start usually shouldn't earn him a spot on this list. But when it's a very hitter-friendly league and that pitcher walks none and strikes out 12 in that outing after tossing one-hit ball over 8.1 scoreless innings with no walks and 14 strikeouts in his last start, it's plenty.
That pitcher is 23-year-old Tanner Peters, who appears to have figured out the Cal League after a rough start (7.30 ERA in five starts). The team's 16th-round pick in 2011, Peters' no-walk, 26-strikeout performance over his last two starts has to have opened some eyes for an organization without a clear top pitching prospect now that Sonny Gray appears to be in the majors for good.
Robert Whitenack, SP, Cleveland Indians
Season stats: 6.85 ERA, 71 IP, 97 H, 38 BB, 39 K in (AA/A+/A-)
Two seasons ago, Whitenack was an up-and-coming prospect in the Cubs organization who dominated in four High-A starts (1.17 ERA, 23 IP, 11 H, BB, 25 K) and was pitching well after a promotion to Double-A (2.39 ERA in seven starts) when his career was put on hold with an elbow injury that required season-ending Tommy John surgery.
When he returned during the 2012 season, he returned to High-A and struggled with a 5.96 ERA in 15 starts. The Indians plucked him off the waiver this past April, then removed him from their 40-man roster a few days later.
As is the case with many pitchers recovering from Tommy John surgery, the Indians were hoping he would eventually return to form within the two-year mark of his injury. That hasn't been the case, at least not as of yet. In his last three starts with High-A Carolina, the 24-year-old has allowed 12 earned runs and 17 hits in 11 innings with eight walks and three strikeouts.
Tyler Glasnow, SP, Pittsburgh Pirates
Season stats: 2.40 ERA, 101.1 IP, 54 H, 52 BB, 147 K in 22 starts
With Gerrit Cole graduating to the big leagues and Jameson Taillon likely on a similar path with an ETA of mid-2014, the title of "top pitching prospect" in the the Pirates farm system could be up for grabs soon. Glasnow, the team's fifth-round pick in 2011, is making a strong case with his dominant performance this season.
Facing the 19-year-old (he'll turn 20 on Friday) hasn't exactly been a walk in the park for Low-A hitters, who have a .154 batting average against him. Every once in a while, a team will string together some hits against him and score some runs, as Delmarva did on August 7th (5 IP, 4 ER, 6 H), but he still struck out 12 hitters while walking only one.
Glasnow bounced back with four shutout innings against a prospect-laden Hickory (TEX) squad over the weekend. He allowed just one hit and one walk while striking out seven.
Starling Peralta, SP, Chicago Cubs
Season stats: 6.04 ERA, 50.2 IP, 51 H, 27 BB, 46 K (A+/A/AZL)
The Diamondbacks thought so highly of Peralta, a 22-year-old who hadn't pitched above Low-A ball, that they drafted him in the Rule 5 draft this past offseason. But despite his potential, they returned him to the Cubs after four very unimpressive outings in the spring (3 IP, 7 ER, 5 H, 3 BB, 0 K).
Things haven't gotten much better during the regular season, as he allowed 20 earned runs in 14 High-A innings before a demotion back to Low-A Kane County. After pitching 13.2 scoreless innings in his first three appearances, the right-hander allowed three earned runs in 5.1 innings in his next game and then things completely fell apart in his last start on Monday, as he allowed nine earned runs on nine hits with four walks in 4.1 innings.
How quickly things can change for a minor league baseball player. Peralta went from Rule 5 pick with a chance at a $490,000 salary if he could pitch well enough to make the big league squad to being a struggling non-prospect in the low minors and possibly looking for a new organization in the offseason.