Much has been made of Glen Perkins' start to the season, since he has seen some pretty great results. Going into the season, I was still skeptical that Perkins could be much better than a replacement-level starter. Have we seen anything that should make me change that opinion?
First, let's check out his pitch selection to see if he's doing anything differently there (data from fangraphs):
| Year | FB (mph) | FB freq | CH (mph) | CH freq | CB (mph) | CB freq | SL (mph) | SL freq |
| 2008 | 90.7 | 70.3% | 83.3 | 15.7% | 76.9 | 7.3% | 82.5 | 6.7% |
| 2009 | 88.7 | 66.0% | 81 | 15.6% | --- | 0.0% | 82.2 | 17.9% |
So Perkins has more or less abandoned his curveball and replaced it with a slider. We also see that his slider's not completely new for this year--he started throwing it last year, probably towards the end of the season. (I'm too lazy to double-check now, but I think there was a report towards the end of last season that talked about Perkins added a slider during the season.) Of course, if he worked on his slider over the winter (and by all accounts he did), it could be better than it was last year.
Next, let's check out his peripherals to see what sort of results he's been getting (from the Hardball Times):
| Year | K/G | BB/G | HR/G | GB% | LD% | OFB% | IFB% |
| 2008 | 4.3 | 2.3 | 1.5 | 38.0 | 22.3 | 36.3 | 3.4 |
| 2009 | 5.2 | 1.7 | 0.0 | 38.9 | 15.3 | 37.5 | 8.3 |
Pretty much better across the board, but more in some places than others. The first thing that sticks out to me is that he hasn't allowed any HR yet and he allowed a lot of HR last year. The second thing is that his K-rate is up some, which is good, but I'm not sure it's up enough that it's a significant change. His line drive rate is certainly down, but most of the people who have looked at line drive rate more closely say that it shifts around a lot, so I'm not sure we can trust it that much. (Conversely, line drive rate for hitters is certainly something that they have a large degree of control over, so it's possible that the hitters Perkins faced had more to do with his line drive rate than Perkins did.)
Finally, let's look at some summary stats (from the Hardball Times and Statcorner):
| Year | xFIP | tRA* | FIP | tRA | ERA | RA |
| 2008 | 5.05 | 5.60 | 5.24 | 5.95 | 4.41 | 4.83 |
| 2009 | 5.25 | 4.95 | 2.89 | 2.36 | 1.50 | 1.50 |
Perkins' FIP is down a lot, which is good, but his xFIP is more important in terms of future expectations, and that's actually up by just a bit. Why is that? xFIP "knows" that Perkins can't sustain that 0.0 HR/G rate, so it uses his FB% to estimate how many HR he's going to allow going forward. We see similar things with Perkins' tRA (which tries to describe his results) and his tRA* (which tries to describe his talent.) His tRA is way down, but tRA* knows that he can't sustain a 0.0% HR rate, so it's much higher. On the bright side, his tRA* is down a little bit from last year, which disagrees with the xFIP result because tRA* takes his (regressed-to-the-mean) line drive rate into account and xFIP ignores line drive rate altogether.
More or less, anyone is going to look great if they don't allow HR, don't allow walks, and have a low line drive rate. Unfortunately, I only see Perkins continuing one of those three things, and even though he's changed his approach, I don't see much improvement. Maybe he's roughly a 4th starter instead of being roughly a 5th starter, but I definitely don't see an ace.
Yeah, we definitely need to see more before getting too excited. Nice to see the K-rate up and the BB-rate down, that's the biggest key for any pitcher. However, Perkins has made all three starts in the pitcher-friendly dome and this last start was against the Angels without Vlad and his first start was against the Mariners without Ichiro. Also, his other start was against the Blue Jays, who have huge platoon splits so far: .892 OPS vs. righties, .767 vs. lefties, although the .767 is still above the AL average of .750 vs. lefties.
Good article, ubes - One question - does it make sense that his xFIP is higher this year with a higher K/9, lower BB/9, and comparable OFB%? (or does the formula only use FB% so the increase in infield flies isn't accounted for?)
Perhaps an interesting point is that if he continues to limit walks (and therefore baserunners) the regression in HR/9 won't be as harmful as it would be with '08 Perkins. I don't know how much improvement that would actually work out to, but so far he's got a WHIP that's well below 1, whereas last year it was at 1.47.
(For the record: In his three starts this season, Perkins' WHIP stands at .833.)
Good article, ubes - One question - does it make sense that his xFIP is higher this year with a higher K/9, lower BB/9, and comparable OFB%? (or does the formula only use FB% so the increase in infield flies isn't accounted for?)
My guess is that the additive constant that they use to adjust everything to league average may have changed. (Their factor for HR per FB may have changed, too.) It's not so much of an increase that I would take it seriously, though--the uncertainty in his 2009 xFIP is certainly larger than the difference between his '08 and '09 xFIP.
What about pitch location? Both Reusse and Len3, I think, focused on the location of Perkins' pitches and the requisite intestinal fortitude required to pitch inside. I'm not interested in that as much as whether there is aggregate data to compare with the first three games of his season. I found a couple tools online, but I'm not sure it's such a good idea to be downloading anything on the work machine with just a few days before I jump ship.
If Perkins does have an intestinal fortitude advantage over other pitchers, then it will show up in his results eventually. Maybe pitching inside has helped bump his K-rate a little higher, but it hasn't really helped him get more ground balls and eventually he's going to give up home runs.
Additionally, I feel like this is a talking point that was borrowed from last year. That is, I don't think that anyone is claiming Perkins had trouble pitching inside last year and is suddenly doing it more this year. My recollection is that he has always been praised for this relative to Slowey and Baker, not relative to his own past performance.
I have no doubt that pitching inside at times has its merits, but at this point it seems more like one of those points that talking heads glom onto and beat to death, making it seem much more important than it actually is.
I think you're right; the "Perkins pitches inside" meme has been around as long as Perkins has been around.