Is Martinez the reliever any different?

Carlos Martinez returned from the disabled list on August 21 as a reliever. The best starting pitcher in the Cardinals rotation would now be used in one- to two-inning chunks. It was a tough pill to swallow with the playoffs approaching, but the Cardinals success since and current hold on the second wild card in the National League have removed most scrutiny from the decision.

When pitchers move between the starting rotation and bullpen characteristics change. Even without numerical evidence to back this up, the hypothesis is based off the approach pitchers take to combat three to six hitters versus 15 or more.

We still have Martinez’s low-three-quarters arm slot and patented crossfire momentum towards the first-base side of the rubber. The elevated levels of medical attention and rehab thankfully haven’t taken his energy and attitude from the clubhouse. But in Martinez’s nine appearances since his return, he has altered some aspects of his game that highlight a change in approach to hitters.

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The interesting thing about Martinez is that his pitch mix isn’t substantially different from being a starter to a reliever. Even the difference we do see—particularly against left-handed hitters—might be full of noise more than anything else.

Since becoming a reliever, Martinez has been matched up versus right-handed hitters at a far higher rate in 2018. As a starter he faced left-handers about 60 percent of the time. As a reliever that number is down to 40 percent. This could be creating a bit of a small-sample issue in Martinez’s pitch mix above. He’s only thrown 61 pitches to left-handers.

The more important takeaway from this change is Martinez facing the handedness of hitter that has given him trouble over the last three seasons at a far lower rate. In each of his last three seasons, the righty has faired worse statistically versus left-handed hitters in nearly every statistic. These struggles could be attributed to the lack of a plus changeup from Martinez in each of the last two seasons along with other peripheral factors.

While there might be some speculation Martinez is now a reliever for medical reasons—which we will never know for certain—the Cardinals could have calculated this starter-to-reliever move from another perspective. As a reliever, it’s more likely that Schildt would be able to match Martinez up against right-handed hitters, with only the occasional lefty pinch-hitter to mess things up. There are strong statistical indicators that the Cardinals knew Martinez would actually be more effective as a reliever.

What management likely expected was a substantial increase in effectiveness because of this ability to match Martinez up in favorable situations. They were right, but yet again the reasoning behind the improvement is interesting.

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Martinez has become more of a fly-ball pitcher than he ever was historically. In his months this season as a starting pitcher, his fly-ball rate ranged between 28 and 38 percent (league median in 2018 is 35 percent). In his two months as a reliever, his fly-ball rate has been between 41 and 45 percent. This might be small-sample error peering its ugly head once again, but the change might hold a candle given where some of his location has trended since his flip.

Compare Martinez’s two-seamer location from his days as a starter to his time as a reliever and you’ll see some elevation. Elevation, more often than not, leads to fly balls. This could be intended, but a stronger hypothesis might be tied to sporadic command. His walk rate might not be higher, but we’ve all experienced Martinez’s struggles in the first inning of games last season. While his mechanics have become consistent over the years, he still possesses the fault of wavering on the mound and leaving viewers to wonder whether he’ll ever throw a strike again.

With all this said, Martinez’s results have been great, suggesting the potentially calculated move by the Cardinals to match him up in better situations has paid off. His ERA is below 2.00 and his sub-3.00 FIP suggests there isn’t much regression to come in his controllable results. He’s stranding runners and getting good defensive play behind him. Most important in late-game scenarios, Martinez isn’t giving up home runs.

That’s where a small issue arises.

The concern for Martinez lies in whether the ability for him to keep fly balls in the park will continue. He hasn’t allowed a home run in his 10 ¹⁄₃ innings of relief work. Incorporating xFIP into our analysis—a statistic that applies a standardized home run rate to conventional FIP—suggests a grim future. His xFIP as a reliever in the month of August was 4.69 and is 4.09 in the month of September. The 1-2 point jump suggests the balls he’s kept in the park will not continue to stay out of the bleachers with certainty.

A fix could be reigning in his command and consistently locating his two-seam fastball low in the zone while leaving his four-seamer elevated. This might keep a potential implosion on a lower tier of possibility as the Cardinals move to more intense September games.

The Cardinals are smart. They calculated how much more effective Martinez would be versus a higher frequency of right-handed hitters and have reaped the benefits. The question is how long it will sustain with Martinez’s new-found tendency for fly-ball contact.