(AP Photo/Tony Dejak)

The Cleveland Indians traded right-hander Justin Masterson to the St. Louis Cardinals, who get a much needed — although ailing — starter.

Masterson, who is 4-6 with a 5.51 ERA in 19 starts this season, has spent the last three weeks on the disabled list because of right knee inflammation and his next start will be his first since early July. He is owed the remainder of a $9.76 million salary for this season and is eligible for free agency this winter.

“I was surprised,” Masterson said. “It’s bittersweet. I’m sad to leave the fellas and the fight we’re making here in Cleveland, but I’m excited to get to St. Louis and be a part of what they have going there.”

The Cardinals are 1 1/2 2 1/2 games behind the Milwaukee Brewers for the NL Central lead and Masterson will need to improve quickly if he is to contribute to a playoff push for the next few months. He is currently striking out fewer batters, walking more and the velocity on his “hard” pitches have been in a free fall this season, making his fourseam fastball worth minus-11.2 runs.

“I think the knee affected him pretty bad,” said Indians pitching Mickey Callaway. “It affected the way he landed and was able to throw against his front side. It probably accounted for the difference in velo (velocity) that we’ve been seeing.”

If healthy, Masterson could provide just what the Cardinals need: a right-handed pitcher who can neutralize right-handed hitting. Here are his splits for the current season:

Seven of the eight most frequent positional starters on the Brewers bat right handed, and it is perhaps no small coincidence that Masterson will make his debut against that squad this weekend.

Masterson has also induced a large number of groundballs this season (58.5 percent), but has a batting average on balls in play of .350. Of the 23 starters qualifying for the ERA title and a groundball percentage of 50 percent or more, just six have a BABIP of .300 or greater. A superior Cardinals defense (measured by Ultimate Zone Rating and Defensive Runs Saved) should help bring Masterson’s BABIP back to a more normal range.

The Cardinals are betting a lot on Masterson’s health, but they did get a starter one year removed from a 14-10 season where he struck out 195 batters in 193 innings for just a non-elite prospect in return. That’s not bad for a rest-of-season ZiPS projection of 3.74 FIP and 0.8 WAR. And with a little bit of luck, it could turn out to be a difference maker.