Via Chad Jennings of the Journal News:

“We threw 16 of them (Wednesday), so I guess so,” Burnett said. “As long as he keeps throwing them down there, I’ll keep throwing them.” In this case, “he” is Burnett’s new catcher, Russell Martin, who’s been calling for the changeup since spring training. “It took me 12 years to throw a changeup,” Burnett said. “He believes in it, and I’m starting to more and more.”

In A.J. Burnett’s first two seasons with the Yankees he was primarily a two pitch pitcher. He had a changeup, but he threw it just a little over two percent of the time. This season has been entirely different. So far he’s thrown the pitch 10.9 percent of the time and it has become an effective weapon falling in for a strike 75 percent of the time.

Using the changeup so much has indirect positive effects as well. With three pitches hitters aren’t just looking fastball or curveball. Now he’s got a third offering and it has made the other two pitches more effective, particularly his fastball.

In his first two seasons with the Yankees his fastball was rated -14.4 in 2009 and -14.3 in 2010. Two seasons where he didn’t throw a lot of changeups. This season his fastball has a positive 1.0 rating.

This isn’t a coincidence either. In the two years where he previously threw a significant amount of changeups, 2005 and 2007, his fastball was rated 7.4 and 8.2 respectively. So throwing the changeup doesn’t just give him a third weapon to utilize, it makes his other weapons better as well. Hopefully he keeps it up.