There aren't too many better stories in baseball this year than the story of Jeff Karstens. A guy who was constantly fighting just to keep a major league bullpen job, he had been sent to the minors a few different times, got another chance this year after the injury to Ross Ohlendor. Karstens took the chance to be a starter and has been one of the best in the league this year.
With a record and a 2.55 ERA, Karstens made it hard to keep his name out of all-star talk. However, his low profile and non-flashy style kept him out of the game without much serious consideration. However, Karstens has the 5th best ERA in the National League and the 7th best WHIP. The basic numbers are fantastic, but when you look a little deeper it's get ugly… or at least uglier.
First of all, let's look into strand rate, also known as left on-base percentage.
Strand rate measures a pitcher's ability to prevent runners he has allowed to reach base from scoring. The major league average is usually something close to 72%, meaning that only 28% of base runners that the average pitcher allows will score.
Now here's the bad news, Jeff Karstens strand rate this year is 88%, which is really, really high, and is basically unsustainable. At some point, more of the runners Karstens allows are going to start scoring, hurting his numbers.
Another statistic we can look at with Karstens is the home run numbers. He has allowed the 5th most home runs in all of baseball with 17. Incredibly, 16 of those home runs have been solo shots, another seemingly unsustainable percentage. The long ball has been a problem for Karstens, but it can only do so much damage when only 1 run scores on it. Some of these home runs are likely to start turning into 2 and 3-run shots and it is going to hurt his numbers and hurt the Pirates chances of winning.
The final statistic I am going to talk about is called FIP, or fielding independent pitching. This statistic gives the pitcher a new ERA-like value looking at only things they directly control. It takes into account home runs allowed, strikeouts, and walks to assign each pitcher a value. Karstens FIP is 4.65, which is 2.10 runs higher than his actual ERA. It's certainly not a surprise to see his FIP being higher than his ERA, but 2 runs is a ton. You can argue this one because the high volume of home runs he has allowed has played a big part in this and his lack of strikeouts has as well, and he has been able to consistently keep those two things from stopping the team from winning, but it's just another sign of bad things to come for the Pirates best pitcher thus far this year.
I know, now is certainly not the time that you would expect negative talk about the Pirates. Positive baseball talk in Pittsburgh is more appropriate right now than it has been for 18 years, but I just couldn't ignore these numbers. Karstens doesn't have great stuff, and there is a reason that everyone is shocked at his performance this year. He has been extremely, extremely lucky and history says he won't keep it up. I don't expect him to go back to his old self of barely being able to hold on to a bullpen job, but I certainly don't expect him to have anywhere near a sub-3 ERA by the end of the year.
Here's hoping I'm wrong. Let's Go Bucs.