Under-the-Radar MLB Acquisitions Proving to Be X-Factors

On a yearly basis, it's the high-priced free-agent signings and blockbuster trades that rule baseball's offseason, not the secondary and tertiary moves that barely register a blip on the radar.

There's a good reason for that, of course. When we're talking about the trade of a perennial All-Star or former MVP in return for a slew of high-profile prospects, or a former Cy Young Award-winning pitcher signing a multiyear contract for an obscene amount of money, it's newsworthy.

But it's often those secondary and tertiary moves that wind up paying the biggest dividends at a fraction of the cost.

While these players may have flown under the radar over the winter, they've been exposed as X-factors and game-changers for their new teams during the regular season—and they're making their general managers look incredibly smart in the process.

Which under-the-radar additions have made the most noise in 2015? Let's take a look.

OF Nori Aoki, San Francisco Giants

Chris Szagola/Associated Press

Nobody viewed Nori Aoki as a replacement in the lineup for Pablo Sandoval, who bolted the San Francisco Giants for the Boston Red Sox as a free agent over the winter. Aoki was more of a complementary piece for the club, which signed the 33-year-old outfielder to a one-year, $4 million deal with little fanfare.

"Aoki gives us speed," Giants manager Bruce Bochy said at Aoki's introductory press conference, via MLB.com's Jane Lee, "and speed is the best way, I think, to replace power."

And he certainly brought speed to the club, swiping a team-high 12 bases and using his legs to provide above-average defense in left field before breaking his leg late last month in a game against the division-rival Los Angeles Dodgers.

But Aoki has turned out to be much more than a speedster for the defending world champions.

His .317 batting average and .383 on-base percentage still lead the team despite his absence from the everyday lineup, and he was a huge reason why the club has been able to handle the extended absence of right fielder Hunter Pence, who has been limited to 18 games this season due to a wrist injury.

In fact, it's fair to say that without Aoki's contributions, the Giants wouldn't be nipping at the Dodgers' heels in a battle for National League West supremacy.

C Francisco Cervelli, Pittsburgh Pirates

Gene J. Puskar/Associated Press

The Pittsburgh Pirates' decision to trade reliever Justin Wilson to the New York Yankees for catcher Francisco Cervelli over the winter wasn't a move met with much fanfare, but it was one that made sense.

Cervelli spent two years (2011 and 2012) learning under Russell Martin, Pittsburgh's former starter who departed for the Toronto Blue Jays as a free agent this past offseason. While asking Cervelli to replace Martin was a stretch, there was hope that maybe he'd wind up being a poor man's version of the All-Star backstop.

Three months into the season, it's safe to say that Cervelli has been far more than anyone expected.

He may not have Martin's power, but Cervelli has been a big-time producer at the plate for Pittsburgh. He leads the team with a .298 batting average, trails only Andrew McCutchen in on-base percentage (.377) and is third behind McCutchen and Starling Marte in OPS (.766).

Per Baseball Prospectus, Cervelli has actually been a more prolific pitch-framer than Martin, and he's come up with some clutch hits to keep Pittsburgh afloat while many of the team's regulars have struggled to get going.

In fact, there's a strong case to be made that it's Cervelli, not McCutchen (or anyone else for that matter), who has been Pittsburgh's MVP thus far.

SP J.A. Happ, Seattle Mariners

Alex Gallardo/Associated Press

If you're looking for an offseason trade that looks completely one-sided at the moment, look no further.

While a knee injury has limited Michael Saunders to nine rather forgettable games in Toronto's outfield, the man the Seattle Mariners received in exchange for him, J.A. Happ, has become a major part of one of baseball's most effective starting rotations.

Happ, who was a part of Seattle's Opening Day rotation, has proven to be a major addition for the Mariners, a team that has been without starters Hisashi Iwakuma and James Paxton for much of the season.

He hasn't been as sharp as he was in April, when he pitched to a 2.30 ERA, but Happ has pitched well enough to keep the Mariners in games, allowing three earned runs or less in 11 of his 15 starts on the season.

That Seattle has gone 6-9 when Happ is on the mound has more to do with a lack of run support than anything the veteran hurler has done while toeing the rubber. And while the Mariners' season may teeter on the brink of being a lost campaign, imagine how much worse things might be if Happ weren't around.

2B Jace Peterson, Atlanta Braves

Mike Zarrilli/Getty Images

Jace Peterson wasn't an afterthought or a throw-in by the San Diego Padres when they sent a four-prospect package to the Atlanta Braves for Justin Upton, but left-handed starter Max Fried and outfielder Mallex Smith were the names fans were most excited about adding to the fold.

By the time spring training ended, Peterson had not only won the Opening Day second base job, but he had also won the hearts of Braves fans and coaches alike.

"Is there anybody that doesn't like Jace Peterson?" manager Fredi Gonzalez rhetorically asked MLB.com's Mark Bowman. "He's an athlete who plays the game with great energy. He can do a lot of things for you with bat, glove and legs."

Peterson isn't setting the world ablaze with his bat, but he's hitting a respectable .267 with a .346 on-base percentage and .720 OPS while providing above-average defense at a premium position and helping to keep a rebuilding Braves club in the hunt for a playoff spot—something nobody expected.

Perhaps most importantly, he's allowed the team and its fanbase to officially put the embarrassing debacle that was the Dan Uggla era behind them, giving hope that maybe—just maybe—the Braves have found their second baseman of the foreseeable future.

SP Chris Young, Kansas City Royals

Thearon W. Henderson/Getty Images

Sometimes, a general manager has to trust his gut instinct, a concept the Kansas City Star's Andy McCullough recently delved into while examining the impact that veteran hurler Chris Young has had on the Kansas City Royals.

"

He [GM Dayton Moore] tasked assistant general manager Scott Sharp with a mission: Go sign Chris Young. He did not care that his rotation was already full and his bullpen was stocked nearly to the brim. He told Sharp to offer Young a big-league contract and hammer out the details.

'We need the guy,' he told Sharp.

Moore cannot discern the source of his impulse. The Royals did not experience an injury the day before. He did not see anything that piqued his interest in depth. He felt something, like a primal need to protect his roster, and acted upon it.

'I just thought that the guy is a winner,' Moore said. 'I felt we were going to need that depth in our rotation. He was out there. You just knew you could trust him.'

"

Young has repaid that trust every time he has taken the mound. After starting the season as the team's long man in the bullpen, injuries to Danny Duffy, Jason Vargas and Yordano Ventura forced him into the rotation, where he's arguably become the team's most reliable starter.

He's gone 6-3 with a 2.97 ERA and 1.09 WHIP over 10 starts, and while he's not giving the team length or striking out batters at a frenetic pace (38 K's in 57.2 innings of work), Young is shutting down the opposition and giving the Royals a chance to win every time he steps on the mound.

That's a pretty darn good return for what began as nothing more than a $675,000 investment—all because Moore had a feeling.

Unless otherwise linked or noted, all statistics courtesy of Baseball-Reference.com and FanGraphs and are current through games of June 30. All contract information courtesy of Cot's Baseball Contracts.

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