At the beginning of the season, Adam Wainwright was the unquestioned ace of the Cardinals' staff. A perennial Cy Young candidate with four top-3 finishes in the last five seasons he has thrown a pitch, Wainwright was an innings monster at the top of his game. After Wainwright went down with an injury that has sidelined him since April, the discussion of replacing him has revolved around a collective effort. Every pitcher stepped up in Wainwright's absence. Lance Lynn pitched incredibly well to start the season, John Lackey has provided effective innings, Michael Wacha has pitched like an ace at various times during the season, and Jaime Garcia came through when nobody expected him to pitch. For much of the season, the Cardinals have pitched without a true ace, a top-10 to top-15 pitcher in all of Major League Baseball, but in Carlos Martinez, the Cardinals are now pitching with an ace as the regular season comes to a close.
Ace is a fairly subjective term. Sometimes it is used to describe the best pitcher on a team, while other times it can mean just the top pitchers in baseball with some slightly arbitrary cutoff (10, 12, 15, etc.). At this point, Martinez is both, but it is important to address the former definition first. Tsunami does lead the team in fWAR, but he is second on the team in bWAR to John Lackey, who has a lower ERA and more innings, leading to an advantage in the latter stat. While this definition is my own, I am defining the Cardinals' ace as the pitcher who has a) pitched the best over the course of the season b) is pitching the best right now c) and provides the most confidence that he will pitch the best in the near future. For me Martinez meets all three categories.
The graph below shows cumulative fWAR over the course of the season by month. fWAR is based principally on FIP, which factors the results we know a pitcher has the most control of: strikeouts, walks, and home runs. FIP is a better predictor of future ERA than actual ERA for pitchers, making it a good combination of describing how well a pitcher has performed as well as telling how a pitcher might be expected to perform in the future. (All numbers below are as a starter)
Carlos Martinez has finally overtaken the team lead in fWAR. Since the beginning of June, Martinez has been worth a full win more than any other pitcher on the staff. It also shows the concern there has been of late regarding Lynn and Wacha. Lackey had a great May followed by solid efforts in every month after, but Martinez looks to be getting better over the course of the season. How much better might be slightly masked by cumulative nature of the fWAR as a counting statistic. The next graph shows strikeout percentage minus walk percentage (K-BB%) cumulatively by month. K-BB% simply takes strikeouts minus walks divided total batters faced. Like FIP, it is also a decent predictor of future ERA.
Carlos Martinez keeps getting better as the season goes on, lowering his walk rates without decreasing his strikeouts significantly. John Lackey has also improved as the year has gone on, but the lack of strikeouts keeps down the list for the Cardinals. If you have noticed, the above stats have not really taken into account what happens when the ball is put in play or whether the pitcher can induce weak contact. It is possible that ERA can take care of some of that, but defense and random variation come into play there as well, which is what makes ERA inexact at telling us how a pitcher actually performed.
We do have some new knowledge with the availability of statcast providing exit velocity on batted balls. The data is not perfect as not all batted balls have been captured with the data, but we do have a significant amount of data, and there are indicators that the batted ball data stabilizes relatively quickly, and lower exit velocity generally leads to fewer hits. Repeating the graphs from above using exit velocity data from Baseball Savant, we see the following results.
There is not a wide range of exit velocities that could make some of the variations seem greater than they are as Lackey, Wacha, and Garcia are all within one mph of where they were at the end of June. Lynn's struggles have been well documented as he has moved up two mph since the end of June, but Martinez has gone the opposite way. While an inflated BABIP in the second half at .357 has caused a relatively unsightly 3.75 ERA, his K-BB% indicates he is pitching better when batters do not make contact, and his exit velocity suggests than when they do make contact, they are not hitting the ball very hard. The 85.4 mph average exit velocity for Martinez is lowest in MLB for those pitchers with at least 100 PA beating out Clayton Kershaw, Jake Arrieta, and Dallas Keuchel, who are also in the top ten. (Feel free to doubt the importance of the stat, but on the year, Clayton Kershaw, Jake Arrieta, Chris Sale, and Dallas Keuchel have the lowest exit velocities in MLB).
On the season, Martinez's ERA, FIP, and xFIP have been stabilized to become nearly identical as a starter. That these numbers are all so close leaves little doubt that Martinez has performed exactly as well as his results have appeared.
El Gallo's xFIP has remained relatively steady throughout the season, slowly falling as the year has gone on while his FIP and ERA both peaked in the middle of May, each going on a sharper decline before meeting up at the present. Martinez had two poor starts in early May against the Cubs and the Pirates, giving up seven runs in each outing and leading some to foolishly question Martinez's viability as a starter. As the season has worn on, his numbers have gotten better and he has gotten stronger. From Brooks Baseball:
The Cardinals have not had to hold back Martinez for any length of time, but have held him back time and again briefly to keep his innings down. He currently sits at just 180 innings on the season and will likely finish at around 190 before the playoffs start. Although he will have a big bump in innings over last season, he has not made over 108 pitches in any start, and he has managed to average over six innings per start despite averaging under 100 pitches per start, indicating fairly efficient, lower-stress innings. Getting Martinez up to 220 innings after the playoffs probably was not the ideal scenario heading into the season, but the Cardinals have ensured that Martinez has not pitched tired, and all indicators say that he is pitching stronger now than at any point in the regular season. (Ben Godar does a good job further explaining why Martinez should not go to the bullpen in October).
Over the last three months, Martinez has made six starts against the Cubs or Pirates (three each). While the rest of the rotation has taken a step back against those two teams, in those starts made by Carlos Martinez, the Cardinals have gone 5-1 while El Gallo has pitched 38 innings, striking out 42, walking 12 with a 3.08 ERA and 2.46 FIP.
As for being an ace in baseball, there are those out there who might pick and choose 10, 15, maybe even 20 starters before picking Martinez, thus arguing he is not an ace. His ERA, FIP, and WAR (either one) are all around the 15-20 mark this season. However, since those two back-to-back poor starts in May against the Cardinals' rivals (his 13th and 14th starts of his career), Martinez has a 2.75 FIP and a 2.57 ERA for the Cardinals in 140.1 innings pitched over 22 starts. This season, only six pitchers have a better FIP than 2.75 and only five pitchers have a better ERA than 2.57 and the only pitchers with both this season are Clayton Kershaw and Jake Arrieta. Carlos Martinez is one of the very best pitchers in baseball, he is the ace of the Cardinals' staff, and he has been pitching like it for quite some time.