Carlos Martinez owns a big difference between his lefty/righty splits. He has only shown one effective pitch against lefties, and if there’s one person who can take advantage, it’s Joe Maddon.

Today, Carlos Martinez and the Cardinals will take on the Chicago Cubs in the first game of a four-game series. Cardinals fans are probably very happy that the team’s ace will be starting, but there is cause for concern. Martinez is a very good pitcher, but he struggles against left-handed batters. Lefties have gotten on base six percent more often and have recorded a wOBA nearly 100 points higher than righties against Martinez for his career. You can bet that Maddon will stack his lineup with lefties tonight.

Righties have a lot of trouble with Martinez’s sinker, changeup, and slider. They aren’t bad against his fastball, but not much power there either. In fact, Martinez has given up just eight home runs to righties for his career. On the other hand, lefties can get the barrel on just about everything aside from his changeup.

Lefties are hitting .179 against Martinez’s changeup, but no worse than .281 against any other pitch. Even more alarming is his whiff rate against lefties. With the changeup, Martinez records a swing and a miss on one out of every five pitches against lefties. The whiff rate on his fastball and sinker are around five percent, while the slider is at ten percent. For comparison, righties swing and miss about twice as often on all three of the fastball, sinker, and slider.

For whatever reason, Martinez just has trouble missing bats with the same stuff. Why is his stuff so much less effective against one side of the plate? Well, some of it has to do with the problem that it is harder for him to get his fastballs in on lefties. He has some natural rightward movement on his four-seam and his sinker obviously moves even more. However, I think more of it has to do with location.

When facing left-handed batters, Martinez tends to throw his fastball and sinker higher in the zone. Check out the difference in location versus each side of the plate. The left side is against lefties and the right side is against righties. These first heat maps, courtesy of baseball savant, are for his four-seam fastball:

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Still in the zone, for the most part, but much higher. Lefties sometimes struggle with higher pitches from right-handed pitchers. However, you don’t want to be living up there all the time, as that is just asking to give up homers. Here is what is happening with his sinker:

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Against righties, Martinez uses the entire side of the plate, going all the way to the knees. Against lefties, he stays at the thigh or the belt. The sinker is most effective against opposite side hitters if you make them dive at the outside corner. If the pitch isn’t low enough, then they can just reach out their arms and slap the ball. Martinez really needs to get that pitch down more, and that will make it harder to get line drives off of the sinker.

His changeup doesn’t show much of a difference, while his slider just doesn’t have enough two-plane break to be as effective against lefties. I don’t think it is a coincidence that his changeup shows the least difference in location and it is his best pitch. He does shift it outside a bit more against lefties, but not as much as he does with the slider.

Should Martinez change his gameplan against lefties to be more like what he does against righties? I don’t really know. I do know that he recognizes that his changeup is his best pitch against lefties. He throws it as his number two pitch against lefties, while it’s his fourth pitch against righties. We have no idea if he would be better if he actually did make the adjustments that I suggsted, but I think it is worth thinking about in the offseason. For now, just let him pitch.

Tonight, though, that could be a problem. Joe Maddon is the best in the business at lineup optimization, and he will know the platoon splits. He’ll likely have all lefties in his lineup except for Addison Russell and Kris Bryant. He’ll likely start pinch hitting righties once Martinez is out of the game. There is a reason that Cubs’ hitters have a .359 OBP as a team against Martinez. This should be a tough matchup for the Cardinals’ best pitcher, but there is some good news.

Even though the Cubs may hit Martinez, the game is not over already. Actually, it’s about even. Cardinals’ batters have a combined .333 OBP against Cubs’ starter Jon Lester with more power than the Cubs have displayed against Carlos Martinez. Lester versus Martinez sounds like a pitchers’ duel, but it may not be. I just worry about Martinez really struggling with only one plus pitch all night against lefties and Joe Maddon in the other dugout.

Photo credit: Joe Nicholson – USA TODAY Sports