Polanco, Grandal among NL players ready to break out in 2015

Can Gregory Polanco turn his potential into a star-making performance in 2015? He's on our list of five breakout players to watch in the NL this year.

Who's going to bust out as a star this year, and who's simply going to bust? Before the start of the regular season, Cliff Corcoran and Jay Jaffe are picking ten players who appear to be headed for breakout seasons and ten players likely to be disappointments. Be sure to bookmark these articles so you can tell them how wrong they were in September. Here are your 2015 NL breakout players.

AL Breakout Players | AL Busts | NL Busts

Travis d'Arnaud, C, Mets

A supplemental first-round pick by the Phillies back in 2007, d'Arnaud became a familiar name long before he reached the majors, as he was a key part of both the '09 Roy Halladay blockbuster trade and the '12 R.A. Dickey deal. A long string of injuries—a herniated disc ('10), a tear in his posterior cruciate ligament ('12) and a broken foot ('13)—slowed his climb through the minors but didn't dim his star: He's the rare player to crack Baseball America's Top 100 Prospects list five times.

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After a 31-game cup of coffee in with the Mets in 2013, d'Arnaud was the Opening Day catcher last year, but he struggled to get going at the plate, missed the second half of May due to a concussion and was sent back to Triple A in early June after batting just .180/.271/.273 through his first 145 PA. He returned 18 days later and hit .272/.319/.486 with 10 homers in 276 PA the rest of the way, including a three-run shot off Scott Kazmir in his second PA back. That showing boosted his offense into the realm of respectability, but his value was undercut by poor defense. D'Arnaud threw out just 19 percent of would-be base thieves, allowed a league-high 12 passed balls and finished with a major league-worst -15 DRS. That said, he was a strong +11.2 runs in the framing department, and a bone spur in his right elbow that was surgically removed in October helps to explain some of his defensive woes.

This spring, the Mets are working to restore d'Arnaud's defense, which hadn't previously been a problem, and have already seen improved results in both his throwing and his pitch-blocking. Between that and a more consistent showing at the plate, the 26-year-old backstop should be an above-average player this year.

Yasmani Grandal, C, Dodgers

At 26 years and three months and heading into his fourth major league campaign, the switch-hitting Grandal is the oldest and most seasoned veteran on this list, though he has yet to have a full, unimpeded season. The No. 12 pick in the 2010 draft by the Reds, he was traded to the Padres just 18 months later and in the majors by June 2012. A midseason arrival who spent time on the disabled list, Grandal played just 60 games as a rookie and just 28 games in '13 due to surgery to repair the ACL and MCL of his right knee, also serving a 50-game Biogenesis suspension that in part coincided with his rehab.

At less than full strength when he returned to action last year, Grandal hit just .210/.299/.364 in the first half before improving to .242/.356/.440 in the second. He finished with just 1.2 WAR but ranked sixth in Baseball Prospectus' pitch framing metric at 17.8 runs above average.

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Between that rocky trail through three seasons, his Petco Park-suppressed offense (.230/.342/.382 at home, .260/.358/.443 on the road), an atypically awful showing against lefties last year and his strong framing stats (+29.4 runs per 7,000 pitches), Grandal offers some upside that may not be apparent at first glance. It wasn't all that surprising, then, to see him become the key part of the Dodgers' return in the Matt Kemp deal, a rare intra-division trade and one pulled off by a pair of general managers eager to make splashes in their first offseason with their new teams. Dodger Stadium isn't exactly a hitters' paradise, but Grandal should benefit with the change of scenery, as well as better health.

Carlos Martinez, RHP, Cardinals

A key reliever during the Cardinals' 2013 postseason run and a pitcher who has drawn comparisons to Hall of Famer Pedro Martinez—no pressure, kid—Martinez entered last season ranked 31st on BA's prospect list (other sites ruled him out due to service time), though it wasn't clear whether he'd wind up in a setup role or as part of the rotation. Given the team's enviable depth, he lost out to Joe Kelly for the fifth starter job and wound up in the bullpen except for a seven-start run in June and July during which he averaged less than five innings per turn, walked 4.5 per nine and posted a 4.45 ERA.

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Martinez was more effective in relief, but didn't quite settle into a setup job until late in the year, and after a brief reset at Triple A in early August, he returned to post a 1.71 ERA and 20/5 K/BB ratio over his final 21 innings. He finished the year with a 4.03 ERA but a 3.18 FIP, with a .343 BABIP accounting for much of the discrepancy. Now, with Kelly gone to the Red Sox and Shelby Miller traded to the Braves over the winter, the Cardinals enter the season with Martinez competing for the fifth starter spot along with Marco Gonzales, who's no slouch himself. With a high-90s fastball, sinker, slider and a changeup that can't help but be better after having worked with Pedro over the winter, Martinez has the potential for four plus pitches.

The Cardinals may have tipped their hand with regards to the rotation race by giving Martinez a locker next to Yadier Molina at the team's spring training complex, suggesting he's got the inside track on the job if he can sharpen his game. He was impressive in his first spring outing, getting ahead of and retiring all six Marlins he faced (including Giancarlo Stanton) and going to two strikes against five. Expect him to build on that, win a rotation job, and begin delivering on his promise, if not the Pedro comps.

Gregory Polanco, RF, Pirates

After a stellar 2012 season in A-ball and a 2013 season that included a trip to Citi Field for the Futures Game, Polanco entered the '14 season ranked 10th on BA's Top 100 Prospects list. Particularly given the Pirates' long struggle to find a productive rightfielder, anticipation ran high that he would soon join Andrew McCutchen and Starling Marte in the big club's outfield, and when he hit .400/.457/.632 in April, it ran even higher. He likely would have been recalled sooner had he not turned down a seven-year, $25 million contract; as it was, the team kept him in the minors long enough to clear the Super Two date in early June.

Polanco began his major league career with an 11-game hitting streak that included a game-winning homer, but inevitably, the league caught up to the 22-year-old prodigy, and after a 1-for-30 slump, he was sent back to Triple A in late August. He made just three starts upon being recalled in September and finished the year with a .235/.307/.343 line with seven homers and 14 steals in 312 PA.

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Given his five-tool potential and the glowing scouting reports he received on his way up, the 6'4", 235-pound Polanco is obviously capable of better than that, and with Travis Snider traded to the Orioles, he won't have to battle for playing time. He's got far too much speed to repeat that .272 BABIP (he was at .341 from 2012 to '14 in the minors) and far too much power to slug below .400 (he put up a .173 ISO in those three years). And while he may not be as good against lefties as righties, he's bound to improve on his small-sample struggles against same-siders (.171/.222/.244 in 91 PA); the Pirates don't appear concerned on that front. Additionally, he should be better rested after playing in 171 games in the minors and winter ball in 2013; the team held him out of winter ball this time around, and instead he worked out with Marte in the Dominican Republic. He should to start living up to the advanced billing very soon.

Kolten Wong, 2B, Cardinals

Wong came into last year as a well-regarded prospect, having hit .303/.369/.466 with 10 homers and 20 steals in 21 attempts at Triple A in 2013, though he went just 9-for-59 in his cup of coffee with the Cardinals and was picked off of first base to end Game 4 of the World Series against the Red Sox. While the trade of David Freese to the Angels and shift of Matt Carpenter to third base cleared a path to the job for Wong, the team brought in veteran free agent Mark Ellis as an insurance policy and showed unusual impatience with Wong early in the season, sending him back to Triple A in late April at a point when he was hitting just .225/.276/.268.

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Wong returned three weeks later and went on a 16-for-42 tear, and while his overall batting line (.249/.292/.388) was nothing to write home about, a 20-for-24 stolen base showing and good glovework (+9 Defensive Runs Saved) enabled him to turn in a 2.2 WAR season. He went 7-for-29 in the postseason with all of his hits going for extra bases, including three homers, two of them game-winners.

Several aspects of Wong's performance suggest there's a whole lot of room for the 24-year-old to grow. His 3.9 strikeout-to-unintentional walk ratio and .275 batting average on balls in play were both out of kilter with his minor league track record (1.6 K/BB and .340 BABIP), as was his reverse platoon split; where he had (unofficially) hit .312/.377/.471 against righties on his way up, he hit just .234/.285/.371 against them last year. More firmly entrenched in the lineup, and certainly more confident, he's likely to show more of what made him a top prospect.