Mike Pelfrey has never been known for his pinpoint control. Throughout the minors and majors he has only stayed under three walks per nine innings once (2.87 BB/9 in 2008).

However, while his tendency to give up the occasional free pass has hurt him in the past, something changed this year that made him a very effective pitcher –that is until a start against the Florida Marlins on June 30  derailed his season.

In his first 14 starts this season, Pelfrey went 10-2 with a 2.71 ERA and a 1.22 WHIP, but has posted an 0-3 record with a 12.89 ERA and a 3.41 WHIP over his last four starts.

Trying to decipher this Jekyl-and-Hyde act isn’t easy, but I’ve sifted through the numbers for you and think I have figured out what has plagued Pelfrey over the last month. First, let’s take a look at his peripheral stats before and after June 30 (July stats do not count his start on July 19).

It’s never a good sign when a pitcher’s strikeout rate decreases steadily every month. This means more contact is being made and with the ballooning walk rate (8.1 BB/9 in July), that means more players on base to score runs. Pelfrey was doing a good job limiting his walks, especially in June (1.99 BB/9 in June), but has gotten away from the approach that worked for him all season—throwing fastballs for strikes. Take a look at the following chart from texasleaguers.com:

Pelfrey has been throwing his fastball fewer times and less effectively. It’s always been said that a good fastball is key to setting up secondary pitches, so could it be that Pelfrey’s ineffective fastball has ruined the rest of his game? It’s clear that batters are being more patient with his fastball (37.8% swing rate in last four games) and Pelfrey is going to have to throw it for strikes more often than 55 percent of the time to make players change their approach.

It’s true that Pelfrey has fallen into some bad luck as he has a BABIP of .483 in July despite a 52.6% groundball rate. With the increase in walks this bad luck has been catastrophic as men are usually on base.

It’s safe to say that Pelfrey is in a funk and there’s no telling on whether he will fix it soon, or at all. He is droppable in shallow leagues, but in deeper formats he should be stashed on the bench until some improvement is shown because you cannot just disregard his first three months.

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