KANSAS CITY, Mo. (AP) -- Royals pitcher Yordano Ventura will miss his next start after an MRI exam taken Tuesday on his sore right elbow showed no ligament damage, while top prospect Kyle Zimmer has been shut down after straining a muscle in his back.
Ventura, whose 100 mph fastballs have made him a rising star, was removed from Monday night's loss to Houston with discomfort in his elbow.
He was diagnosed with a mild valgus extension overload, a condition in which the repetitive stress on the elbow can cause pain in the joint.
''We had a pretty good idea exactly what would show up on the MRI and that's exactly what happened,'' Royals manager Ned Yost said. ''He's totally asymptomatic today, which means he doesn't feel anything, but as a precaution we'll skip him one start.''
Trainers went out to examine Ventura in the third inning when they noticed a decrease in the velocity on his fastball. But they were confident there was no ligament damage when Ventura said the pain was on the outside of the elbow, rather than on the inside of it.
''It happens. It happens to everybody. It happens to infielders, it happens to outfielders. It's just a freak thing,'' Yost said. ''The pain was on the other side of the elbow, and he only felt it on extension on his fastball. He didn't feel it on his breaking ball or his changeup.''
Still, Ventura said he was concerned about his first elbow injury.
''It felt a little unnatural in my arm and I didn't know what it was, but thank God after the treatment I was able to feel better,'' he said through a translator. ''Right now I don't feel any pain, and I'm very grateful to God and the trainers because they're working with me.''
The plan is for Ventura to rest for the next three days, and then throw two side sessions while skipping his next start. Yost believes he will then be ready to rejoin the rotation.
Yost said he was still considering options for his Saturday starter in Toronto.
Meanwhile, Zimmer will not play catch for at least six weeks after straining a muscle in his back. The fifth overall pick in the 2012 draft, Zimmer was already taking a conservative approach to the start of the season because of biceps tendinitis.
Zimmer was a longshot to win a job out of spring training, but the Royals were hoping he would pitch well enough in the minors this summer to get a call-up to the big leagues.
''Down the road, maybe after the All-Star break if Kyle was throwing good, he might be a guy that we could bring up and help us, and even deep as into September if he was throwing good,'' Yost said. ''We'll see how it goes from here.''