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How Tom Koehler has become Miami’s second half ace

Tom Koehler has been the Marlins best starting pitcher since the all-star break, but what has made him so effective?

MLB: New York Mets at Miami Marlins Steve Mitchell-USA TODAY Sports

Everyone knows that if you are looking for the ace of the Miami Marlins staff, you look no further than Jose Fernandez, but so far in the second half of 2016, that has not been the case. The best pitcher for the Marlins since the all-star break has been Tom Koehler, who has posted a 2.19 ERA and a .184 batting average against in six starts since July 16. So, how has he been so successful? Let’s take a look.

After posting a WHIP of 1.563 in the first half, Koehler has pitched to a WHIP of only 0.946 in the second half, and that big drop has a lot to do with his decrease in walks. Koehler’s 4.59 walks per nine innings were not very good, but he has been able to get that BB/9 number down to 2.43 in his last six starts.

Although the walks have gone way down, Koehler is not necessarily pitching inside the zone much more often. In fact, he has thrown a lower percentage of pitches (41.7%) in the strike zone in the second half of the season than he did in the first half (43.6%).

What Koehler has been able to do since the All-Star break is get hitters to chase pitches out of the zone much more often. In the first half, batters were only swinging at 25.5 percent of Koehler’s pitches out of the strike zone. In the second half, though, batters are chasing Koehler’s pitches out of the zone 36.6 percent of the time, which ultimately leads to his higher strikeout rate and lower walk rate.

Koehler’s success out of the strike zone may be due to his increased use of his secondary pitches so far in the second half. He was throwing his fastball about half of the time in the first, but he has only thrown the heater 42.6 percent of the time since the break. His breaking pitches, on the other hand, have gone up in frequency. Koehler’s slider usage has jumped from 21.3 to 25.0 percent and his curveball usage has grown from 20.5 to 25.0 percent. Hitters may be used to a more fastball-heavy Tom Koehler, and his increased usage of his breaking pitches could be the reason why opposing hitters are being fooled and chasing many more of his pitches outside the zone.

Along with the success Koehler is having outside of the strike zone, his stats inside the zone have also gotten better. When batters were swinging at Koehler’s pitches in the zone in the first half, they were making contact 88.3 percent of the time, but are only making contact 84.5 percent of the time in the same situations since the All-Star break. And overall he is just missing bats much more often in the second half. His opponent contact percentage has dropped from 79.8 to 71.7 percent, which can also be somewhat attributed to the increased use of breaking pitches.

With the recent struggles of guys like Jose Fernandez and Andrew Cashner coupled with the injuries to Adam Conley and Wei-Yin Chen, Miami needs a starting pitcher to really step up during this stretch run. If Tom Koehler can continue to be a stopper by mixing his pitches and missing bats, other guys will find their groove, and the Marlins will be able to stay in the NL Wild Card race all the way to the end.