Team officials were awaiting results from an MRI to determine the severity of Kazmir's injury, and manager Bob Melvin couldn't rule out a possible trip to the disabled list for the veteran left-hander.
"We'll have to see where he is tomorrow," Melvin said following Oakland's 3-2 loss to the Detroit Tigers. "He probably felt like he could continue to pitch but it didn't make any sense to. You could tell he was a little uncomfortable after the last pitch when he was coming off the mound. His body language wasn't great so we didn't want to push him."
Kazmir, winless since April 13, didn't allow a hit in three innings and struck out four with three walks. He walked slowly off the mound after striking out Miguel Cabrera to end the third, then later was taken to get an MRI on his left shoulder.
"His body language on the mound wasn't good," Oakland catcher Stephen Vogt said. "It was more grimace-y, just kind of like tight. That's how he described it, that his shoulder was tight."
The Associated Press contributed to this report.
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