We are excited to have Corinne Landrey join the FanGraphs writing staff. She’ll be contributing here several times per week, and is going to be an excellent addition to the site. Below is her first post as a FanGraphs author.

If you know one thing about Cole Hamels beyond his profession or employer, it’s likely the fact that he throws a magnificent changeup. It’s the pitch upon which Hamels’ impressive career has been built from the moment he made his major-league debut as a 22-year-old kid. Like any successful pitcher, Hamels has had to adjust and improve over the years first by refining his curveball and later adding a cutter to his repertoire, but the changeup has been the omnipresent ace up his sleeve throughout his major-league career. Until now, that is.

For the first time in Hamels’ decade-long career, his changeup is no longer serving as his go-to secondary pitch. That honor now belongs to the cutter he began using in 2010 after watching his teammate Cliff Lee use the pitch with tremendous results down the stretch the previous season. Since then, the pitch has developed into Hamels’ preferred third pitch and now its usage has officially surpassed the changeup:

This year Hamels has gone to the cutter 202 times, or on 24% of his pitches, whereas the changeup has been used just 185 times, or 22 percent of the time. This usage shift, however, is not the result of a season-long trend. In fact, during the month of April, Hamels threw his changeup more than he threw any other pitch, fourseamer included. But after his start on April 20th, something changed.

Hamels missed his next start due to an injury described unpleasantly as “left groin soreness” and returned to the mound on May 1st. In the month of May, Hamels made six starts and threw 618 pitches, just 104 (17%) of which were changeups. It marked the first time in his major-league career that he threw changeup less than 20% of the time over the span of a full month. So what’s going on? Why is Hamels moving away from his moneymaker? Is it even fair to conclude that he’s moving away from it?

The first and most obvious variables – velocity, movement, release point – yield no compelling explanations. By these basic PITCHf/x indicators, his changeup is largely unchanged from the dominant pitch it’s been throughout his career, the only slight exception being that the pitch has about an inch more vertical drop than it did last season. This is good news! Hamels isn’t shying away from the pitch because he suddenly forgot how to throw it. The Hamels changeup we’ve been watching for years still exists, if only less frequently at the moment.

There is one big thing that has changed, however, and that’s the location of his changeup. Let’s take a look at heat maps of the pitch, courtesy of Baseball Savant, starting with the month of April:

And now look at his changeup location in the month of May:

His changeup location has transitioned from steadily located in prime whiff-zone just below the zone to a wildly inconsistent offering. More than perhaps any other pitch, the changeup is described as a “feel” pitch, which is a scout’s way of saying the subtleties in the grip and delivery of the pitch make it challenging to develop consistency with it. Master that subtlety and you’re said to have “feel” of the pitch. The fact that Hamels developed feel of his changeup at such an early age is part of why he was regarded as a special young talent when he arrived in the majors, but right now it looks alarmingly like he’s lost that “feel.”

The biggest sign that Hamels hasn’t been comfortable with his changeup lately is that he’s all but abandoned it against left-handed batters. Although changeups are often primarily used against opposite-handed opponents, Hamels’ changeup is such a dominant offering that it’s been successful against same-side opponents, as well. Lefties are batting just .196 against his change since 2007. As a result, Hamels has generally gone to the changeup 15-25% of the time against left-handers, but this year he’s thrown changeups on just 6% of pitches to lefties.

On April 20th, the last pitch Hamels threw to a lefty was a changeup to Jason Castro for a swinging strike three. Over his next five starts, he threw 73 pitches to lefties and not a single one of them was a changeup. It wasn’t until the third time he faced Gregory Polanco in his most recent start that he finally unleashed a change against a lefty. Interestingly enough, he followed that changeup immediately with another one, representing his only two changes against left-handers for the entire month.

Throwing changeups to same-side batters can be dangerous because the arm-side run of the pitch can cause it to run directly into the opponent’s bat, but Hamels’ “feel” of the pitch has historically given him the confidence and command necessary to make it a legitimate offering regardless of the handedness of the batter. The fact that he’s avoiding the pitch to lefties now is a glaring sign that he’s not currently as comfortable with the pitch as he has been throughout his career.

The news isn’t all bad — far from it. Hamels has demonstrated an impressive ability to adapt and succeed without his best stuff. In 37 innings during the month of May, Hamels struck out 44 batters and walked just 12. He did run into difficulties with the long ball, however, allowing eight homers (including three on changeups) which contributed to 21 runs allowed, 16 of which were earned, and a resulting ERA of 3.89. That’s a mediocre figure under normal circumstances, but hardly the disaster one might expect from a pitcher who is struggling with his best pitch. An important part of his success this season to date has been the fact that his cutter has picked up the slack for his changeup, with opponents currently hitting a measly .171/.277/.268 against the cutter.

Overall, Hamels currently sports the best contact rate (71%) of his career and the best strikeout rate (25%) since his rookie season. He’s making do with his diminished arsenal, which is promising, considering there’s no reason to expect his changeup won’t come back. Whenever his feel of the changeup returns, Hamels will be in position to go back to pulling strings and Bugs Bunny-ing his way through lineups — this time with the added knowledge that he has the ability to succeed without his signature pitch.