"It was more pronounced [Wednesday] than at any point that he's brought it up," Ventura said. "Definitely at the point where we need to take care of this."
Petricka had been a productive part of a Chicago bullpen that entered Thursday leading the Majors with a 1.75 ERA, but he did struggle in his April 28 outing against the Orioles, when he gave up four runs (three earned) in one inning during a 10-2 loss.
That outing pushed his season ERA from 1.35 to 4.70. In his latest appearance, Petricka yielded a hit and a walk in one-third of an inning.
"This is something that had to happen," Ventura said. "We weren't going to be able to use him for a week at least to be able get over this. The way he's throwing, you want him back to feeling 100 percent, so you're not going to go injure anything trying to protect it."
The White Sox filled Petricka's spot with 26-year-old right-hander Tommy Kahnle, who will make his second Major League stint this season. Kahnle threw a scoreless inning in his only MLB appearance this season last Friday against the Orioles.
Kahnle was 1-0 with a 2.45 ERA and 13 strikeouts in 11 innings this season with Triple-A Charlotte. He said he has made notable progress on developing a third pitch in addition to his fastball and changeup, and commanding the slider is his biggest focus going forward.
"It's good to get called back up," Kahnle said. "Any chance you get is going to be exhilarating."
• Avisail Garcia returned to the lineup Thursday after missing four straight games with a strained right hamstring. Garcia had been progressing and said he knew he was ready after working out Wednesday.
"He says he's ready to go," Ventura said. "They tested him pretty good yesterday."
• Injured catcher Alex Avila said he is headed to Triple-A Charlotte and will likely begin a rehab assignment Friday. Ventura said Avila's projected return to the White Sox is to be determined. Avila went on the DL April 24 with right hamstring tightness.
Cody Stavenhagen is a reporter for MLB.com based in Chicago. This story was not subject to the approval of Major League Baseball or its clubs.