Filling the St. Louis Cardinals rotation: Carlos Martinez or Marco Gonzales

Adam Wainwright, Lance Lynn, John Lackey, and Michael Wacha will likely fill the first four spots of the 2015 Cardinals rotation. After sending Shelby Miller (and Tyrell Jenkins) to Atlanta for Jason Heyward (and Jordan Walden), a rotation spot opened, and all signs point toward a spring training competition between Carlos Martinez and Marco Gonzales. Last spring, Martinez was supposedly given a shot against Joe Kelly, but despite Martinez having a better spring and significantly more talent than Kelly, he "lost" the "competition" and was sent to the bullpen.

This spring, unless Jaime Garcia somehow proves his health and the organization wants to see what they have in their $9.375 million arm, it appears we will witness a much truer competition between two exciting, but very different young arms. The Red Baron provided us with 2,500+ thought-provoking words on the rotation last Saturday, but this post will be dedicated to the two young pitchers mentioned above, with an increased emphasis on available PITCHF/x data via BrooksBaseball.

Pitch usage percentages and wOBA splits

The case for Martinez

As Harry Pavlidis told us on Monday, Martinez has the best two-seamer on the staff, and at an average velocity of 96.44 MPH with roughly 13 inches of dragless horizontal movement, it is nearly impossible to disagree with this sentiment. During his two-year MLB career (117.2 innings pitched), hitters have a .057 ISO against his two-seamer, and the only pitch in his arsenal that has prevented more extra base hits than his two-seamer is his changeup, with an incredibly low ISO of .029 (one must note sample size, though, as only 35 ABs have ended on his change). This is the same changeup that resulted in whiffs on 44.07%(!) of swings last season. Thus, that's already two plus pitches for Martinez, with the possibility of both being the best of their kind on the staff.

At present, his 98.19 MPH four-seamer with seven inches of dragless horizontal movement is his most-used pitch (43.86%), and with those two characteristics, who can really blame him? However, with question marks about his ability to average five or six innings per start over the course of a 162-game season, should he be looking to his two-seamer more often? Compared to his four-seamer, it results in more balls in play (23.00% vs. 18.90%) and predictably more ground balls (16.43% vs. 8.46%) as well. Fans of his repertoire blowing hitters away for a strikeout won't have to worry either as the overall whiff rate on his two-seamer (10.88%) is actually slightly higher than that of his four-seamer (8.79%).

Of note, Martinez has yet to allow a home run on his two-seam fastball. In fact, he has allowed only five home runs total since his arrival in St. Louis. In my opinion, if his four-seamer use and his two-seamer use meet somewhere in the middle next season (with his two-seamer use nearing 30% or more), his overall efficiency will increase without negatively affecting his performance—something I am sure Mike Matheny, Derek Lilliquist, and Yadier Molina are well aware of already.

It is a testament to Martinez's repertoire that I have gone this long without a single mention of his slider—a devastating pitch he has used twenty-five percent of the time. When compared directly to his two-seamer, the horizontal movement on his slider is over 20 inches in the opposite direction (in to lefties/away from righties). A twenty inch differential between two oft-used pitches is no joke—leading to weak contact (.071 ISO) and a lot of swings and misses (46.11% to be exact).

Thus, Martinez has the potential to flash four plus pitches at any time (which is more than enough for a successful starting pitcher), and some minor tweaking in game-calling by Molina should lead to increased efficiency—the biggest hurdle left for Martinez to clear. With the final rotation spot up for grabs, will the Cardinals allow for what many at Viva El Birdos so desperately want?

The case for Gonzales

The biggest issue present with Martinez doesn't appear to be a problem for Gonzales as he averaged over five innings per start in the minors despite the Cardinals likely being conservative with his usage. Including the minors, MLB regular season, and MLB post-season, Gonzales threw 186 innings in 2014—just his second season as a professional. Being in the relief role obviously helped, but Gonzales had some of his best stuff at the end of the season, and this carried into October. This is a promising sign for a long season in the rotation.

As I have written in the past, Marco's best pitch is his changeup, and given that he is still establishing his fastball at the big league level, I'm not sure it has realized its full potential just yet. Upon further review, very early returns have the ISO against his four-seamer (.091) slightly better than the ISO against his changeup (.106), though both are quite good. His fastball may only average 90.56 MPH, but he has shown the ability to ramp it up to 93 MPH when necessary, and it appears much faster to hitters when thrown after consecutive changeups.

Something I would like to see from Gonzales in 2015 and beyond? Some cleaning up of his vertical release points. During his short time in the big leagues last season, the vertical release points of his four-seamer and changeup differed by 2.64 inches. This may not seem like much, but with video and repetition of competition, a pitch that largely relies on deception (the changeup) needs to avoid all possible hindrances. If he is able to close the gap between these two, even slightly, both pitches will be experience even more success, especially the third time through a batting order.

A repertoire of two pitches is not enough for a pitcher to be successful as a starter, right? Well, it depends, but this isn't something we need to worry about with Gonzales as he also has two versions of a breaking ball in his back pocket. Neither pitch is fully refined just yet, but he leaned harder on his slider as the season progressed, and it had a considerable amount of success. What surprises me about this pitch is that it actually backs up a little bit, but it maintains enough of a differential from his "straight" pitches to still fool hitters.

Finally, the obvious: Gonzales throws from the left side. Though I have never really believed that every rotation needs a left-hander as long as it has the team's five best starters, there is still a crowd of people out there that believes this is rather important, especially when facing lineups stacked with left-handed bats. Will the Cardinals be more comfortable going with more of a "known quantity" in Gonzales?

Bottom line

When the Cardinals break from Spring Training in early April 2015, I am not sure who will be the Cardinals fifth starter. As mentioned earlier, if Garcia is "healthy," given his contract, it very well could be him. Yet, if Mozeliak's response to the fourth question in this post is any indication, the club's current plan is to move forward without expecting much from Garcia as his status is "TBD." As Heather (lil_scooter93) so kindly pointed out on Twitter, Tyler Lyons may be considered a darkhorse candidate, and though I have been impressed with his repertoire in the past, I think the club would be more inclined in seeing what they have in Martinez and Gonzales first. Given the uncertainty of both Wainwright's and Wacha's health, I wouldn't be all that surprised if all four pitchers I just mentioned receive at least a handful of starts in 2015.

Credit to BrooksBaseball for the data used in this post.