Kevin Slowey: Lucky or unlucky for the Miami Marlins?

The Miami Marlins pulled off a 2-1 walk-off victory last night against the New York Mets, but with the way the team's offense was sputtering throughout the evening, it was a surprise they were even in that contest in the ninth inning. The Fish were bailed out by yet another strong performance by starting pitcher Kevin Slowey, who made the roster as a non-roster invitee and "last man in" the Marlins rotation but is coming off like a revitalized ace. Slowey's eight-inning performance has brought his season ERA down to 2.15 and his FIP down to 3.15.

This prompted an article by David Miller of Rant Sports regarding Kevin Slowey and his "bad luck."

If you take a look at his stats don’t stop at the win-loss column. That would do a great injustice to Slowey’s work this season. The debut game of the season he gave up one run to the Washington Nationals and lost. In his second outing he gave up two runs to the Atlanta Braves and lost. Since then he has had four straight no-decisions. Guess how many runs he has given up over the course of the four no-decisions.

The answer is six runs over 25 1/3 innings. Yes, that is quite an impressive feat, but Miller refers to Slowey's performance as "bad luck" because of his win-loss record. Through six starts, Slowey is 0-2 with four no-decisions to start the season. In terms of pitcher wins, I guess this would qualify as "bad luck."

The reason behind this supposed bad luck in the pitcher wins category is run support. The Marlins have been the worst offense in baseball through April, and that has not changed with Slowey on the mound. The Fish have scored just eight runs in Slowey's six starts, including two shutouts to begin his season. That translates to a rate of 1.3 runs per game. It is very difficult to pick up pitcher wins with that kind of run support.

But here at Fish Stripes, we know that already. We do not care about pitcher wins precisely because it is so tied to the performance of the rest of the team that it is not meaningful for the individual pitcher. Take a look at Slowey's individual numbers, and particularly the statistics that pitchers can best control, and you can see a pitcher who has performed very well but actually has been luckier than expected.

The first place to go is to look at the difference between his ERA and FIP. That difference shows that some factor is helping Slowey outperform his run prevention based on strikeouts, walks, and home runs, the statistics FIP utilizes to estimate ERA. FIP uses these statistics because they are the stats most controlled by the pitcher himself, independent of the defense behind him. FIP expects him to be a 3.15 ERA pitcher, but he actually has an ERA a run lower than that. How is he doing it?

A look at his left on base (LOB) percentage, or strand rate, can tell you that answer. Slowey has stranded 86.6 percent of runners that have reached base against him. That mark ranks 10th in baseball among qualified starters. That might sound like a good thing, except that performance in stranding runners often regresses heavily to the mean within a season. A player may be stranding runners well now, but it does not mean he will continue to do so going forward, and there is a much better chance that he will move towards the league average of 71 to 73 percent as we go on.

Furthermore, the way Slowey has been stranding runners is not indicative of future success either. With the bases empty, he has struck out 23.2 percent of hitters while walking just 3.2 percent of them. This would indicate a dominant performance, except that he is also allowing a .264/.295/.505 line (.341 wOBA) in those situations, thanks to his two home runs. Somehow Slowey has managed to pitch better with runners on base despite worse peripherals. He has not allowed a home run with runners on, but he also has just a 13.0 percent strikeout rate and a 4.6 percent walk rate with men on base. His saving grace is that the defense has helped him in a big way, as hitters are hitting .186 on balls in play with runners on against Slowey. This sort of "clutch" pitching is not predictive of future performance either.

Slowey's wins and losses may be unlucky, but his actual performance is likely very lucky, especially when you consider that his significant past history of giving up home runs has not surfaced yet (1.3 percent home run rate thus far versus a career 3.6 percent rate). But let's not toss Slowey into the "small sample size luck" category yet. Even if you adjust Slowey's home run rate to his career rate, he is still expected to have a 3.70 ERA. While that is not as fantastic as his ERA now, it is still more than serviceable for mid-rotation starter. Slowey may be on his way to a 2.5-win season with that kind of performance, and the Marlins would be extremely happy with that from a non-roster invitee.

Slowey may be unlucky in wins and lucky in performance, but if he keeps up his current strikeout and walk rates, there is a very good chance the Marlins will be very lucky to have picked him up.