Ventura exited Game 2 of the AL Championship Series at Baltimore.
Ventura was facing Caleb Joseph in the sixth inning when he winced and walked off the mound after throwing a pitch.
After a quick visit from the Kansas City trainer, Ventura left the game and was replaced by Brandon Finnegan.
Ventura exited with the score tied after giving up four runs and five hits in 5 2-3 innings. He walked three - all in the second inning - and struck out three.
Back in May, Ventura was led off the field by a trainer because of a sore elbow in the third inning of a start against Houston.
An MRI exam at the time did not show any major damage, but Ventura missed his next scheduled start.