It wasn’t long after the end of the 2014 season that general manager John Mozeliak and manager Mike Matheny informed Carlos Martinez that he’d report to spring training as a starter in 2015.

It was the same message Mozeliak had for the 23-year-old right-hander after the 2013 season.

But after losing to Joe Kelly last spring, Martinez seems to have an inside track toward the final spot in the team’s Opening Day rotation this time around, a spot made available through the trades of Kelly and Shelby Miller.

Armed with a triple-digit fastball and a deep arsenal of swing-and-miss offerings, Martinez has emerged as one of the more dominant late-inning relievers in baseball, making 70 appearances out of the Cardinals’ bullpen since arriving on the scene in May 2013.

Yet the organization has never given up on his upside as a starter. It’s probably because the right-hander showed huge potential in the role during his time in the minor leagues, with a 2.61 ERA, .215 opponents’ batting average and 10.3 strikeouts per nine innings in 338 innings over 69 starts (70 appearances overall).

Martinez has started eight games for the Cardinals over the last two seasons, but his inconsistency in the role as well as the organization’s pitching depth have kept him from locking down a spot in the rotation.

This year, however, Martinez is determined to break camp as a starter. He spent part of the offseason playing in the Dominican Winter League, where he pitched to a 2.25 ERA with 26 strikeouts against two walks in 24 innings (five starts), and he’s already received glowing reviews from members of the organization after reporting to spring training ahead of schedule.

“A year ago you’d just see a kid bounding around here. It’s amazing the transformation,” Matheny told The Associated Press (h/t Fox Sports Midwest) earlier in the week. “In general there’s a whole different demeanor to him.”

So will this be the year Martinez finally sticks as a starter?

As a reliever, Martinez throws mostly fastballs, both four-seamers and sinkers, and sliders, and they’re each extraordinary pitches by all measures.

Martinez’s average fastball velocity of 96.7 mph in 2014 was tied for third highest among all pitchers with at least 80 innings pitched, per FanGraphs, while Brooks Baseball says he topped out at 101.97 mph last April.

Unsurprisingly, Martinez also throws his sinker (or two-seam fastball) exceptionally hard, averaging 95.2 mph with the pitch. He can struggle to control the pitch (17.78 percent strike rate) but generally keeps it down in the zone, as only seven percent of the balls put in play last season against his sinker were in the air compared to 65 percent on the ground.

So what makes the 23-year-old’s sinker so good? Beyond throwing it harder than most other pitchers, Martinez’s sinker stands out for its difference in vertical movement relative to his four-seamer. Specifically, the right-hander’s fastball averaged 8.2 inches of vertical movement last season where as his sinker had 3.2 inches, meaning there was more than a five-inch gap between pitches.

And then there’s Martinez’s slider, which was his best swing-and-miss offering last season thanks to a 24.2 percent whiff rate, per Brooks Baseball. In general, his slider generated whiffs on 45.5 percent of all swings. Martinez’s success with the pitch might have something to do with the fact he threw it nearly five miles per hour harder last season (86.5 mph) than he did in 2013 (81.6 mph), as it also allowed him to create more vertical movement.

Martinez’s changeup was widely viewed as his best secondary offering during his rise through the minor leagues, but he’s had to dial back his use of the pitch significantly as a reliever. But while the right-hander threw it only 2.9 percent of the time, he still was able to produce a nearly 21 percent whiff rate.

Improving his changeup has been a focal point for Martinez this offseason, writes Derrick Goold of the St. Louis Post-Dispatch:

It’s a circle changeup and it has depth to it. The changeup is not a new pitch for him. There was a time during his development that a scout told me Martinez could get “changeup happy” when he should just pile-drive the fastball. Played off his fastball, the changeup was viewed was one of his best and most deceptive pitches as he worked his way through the minors.

But for as good as Martinez’s stuff is, the 23-year-old still has plenty of room for improvement in terms of his command, evidenced by his 3.63 walks per nine innings last season.

The bigger issue is Martinez’s career splits, as he’s dominated right-handed batters in the major leagues but struggled mightily against lefties.

More specifically, he has problems throwing strikes and induce whiffs from left-handed hitters like he does righties:

Combine all that with the concerns regarding his long-term durability as a starter, and you begin to see why the Cardinals want Martinez to earn his spot in the rotation this spring. His main competition is left-handers Jaime Garcia and Marco Gonzales, and it’s possible that Carlos Villanueva could also receive consideration should the other hurlers struggle.

However, none of them have as much upside as Martinez.

Few do.

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