Is he the guy who was 9–1 with a 2.39 ERA in his first 14 starts of the season?Sadly, I think the answer is simpler than people make it out to be.
Or, is he the guy who is 2–6 with a 7.98 ERA in his last eight starts?
I don’t know the answer. I do know he’s getting roughly the same level of strikes he was getting in the start of the season. However, the opposition is hitting more line drives and less ground balls, and more of those line drives are falling in for hits, compared to the start of the year.
So, it would seem he is making more ‘mistakes,’ be it with command or location… and when he does, he’s paying for it.
According to fangraphs, Pelfrey has been almost identially the same pitcher over the last three seasons. His xFIP, by season:
Why am I looking at xFIP? And what is it? According to Matthew Carruth of Fangraphs:
One of the more difficult puzzles to crack has been evaluating pitchers due to how entangled their performance is with that of their defenders. Accepting the move from ERA to Fielding Independent Pitching is probably the single biggest step one can take on the right path of separating the two, and Simmons has made that leap.
Home Runs allowed, an important input to the FIP formula, are not as skill-based as had been thought throughout history. ... xFIP exists to correct those home run rates. It is simply the FIP formula with an expected home run rate based on fly
ball totals, rather than actual home run rate.
xFIP is just a slightly more advanced form of FIP, which is an improvement on ERA because it corrects for luck and the influence of defense, and evaluates pitchers solely on things they can control.
According to FIP and xFIP, Pelfrey has been basically the same pitcher for the last three seasons, with flucutations based somewhat, if not mostly, on random variation. For a guy who allows so many balls to be put in play, this is to be expected.
Is he as good as he was early this year? Is he as bad as he has been recently? Probably neither. A realistic view of the numbers shoudl have indicated all along that his early season improvement was an outlier.
For what it is worth, I believe that part of Pelfrey's early success this year can be attributed to his additional confidence and the addition of the splitter. Because of this, I don't think he's necessarily a 4.50 xFIP pitcher permanently. He's still young, and will improve and learn, but he's certainly way closer to a 4.50 pitcher than a 3.00 pitcher right now.
 Also worth noting, we first discussed Pelfrey, xFIP and tRA back in December right here on Fonzie Forever:
The thing about Mike Pelfrey that confuses me, is why everyone expects him to be good. He's never shown us anything. His best stretch ever was in 2006 in AA, when he posted a 2.71 ERA. The next year, in AAA, he was getting hit around at a 4.01 ERA and 1.35 WHIP pace. There was room for growth, but as a 23-year-old, he didn't have the makings of an ace.
I was glad when [Pelfrey] broke through in 2008, but I wasn't really expecting it. The truth is, he was a little lucky in 2008 and a little unlucky in 2009. His tRA (a metric which is available on fangraphs and is explained here) has his tRA as 4.49 in '08 and 4.52 in '09. And all things considered -- like, with what we saw with our naked eyes -- Pelfrey was very much the same guy. The real difference between that year and this one was that more hits made it through the infield and less guys got stranded on base - his fastball was the same speed, he walked and struck out about exactly the same number of batters.
I see Pelfrey's luck turning again this year, at least back to average.