Zimmer's season halted by Royals

All things considered, it was an impressive first full professional season for Kyle Zimmer. But now it is over.

The Royals announced that they were shutting down their top prospect after he experienced shoulder stiffness in his start with Double-A Northwest Arkansas on Wednesday. The 21-year-old right-hander finishes the year with a 4.32 ERA and 140 strikeouts and 36 walks in 108 1/3 innings (22 starts) between Northwest Arkansas and Class A Advanced Wilmington this season.

"Kyle has some minor shoulder irritation and has reached his innings threshold for the season, so he will no longer pitch in 2013," Royals director of player development Scott Sharp told MLB.com. "He is returning to school for the fall semester to rest and knock out some classes, and will return ready to go in 2014."

Drafted by Kansas City as the fifth overall pick in 2012 out of the University of San Francisco, Zimmer experienced an up-and-down campaign in the Carolina League. On June 7, his ERA sat as high as 6.32 following his third straight start having allowed five runs or more.

"It just seemed that, throughout that stretch, one inning I'd be rolling and then I'd give up a three-spot on some infield hits and then a big hit," Zimmer told MiLB.com of his struggles.

He recovered nicely in July with a 2.50 ERA and an astounding 30-1 strikeout-to-walk ratio over three starts (18 innings), leading to the promotion to Double-A.

The San Francisco native carried that success into the Texas League, where he went 2-1 with a 1.93 ERA, 0.86 WHIP, 27 strikeouts, five walks and .162 opponents batting average in four starts for the Naturals before being shut down. He pitched two perfect innings (23 pitches) against Corpus Christi on Wednesday -- an outing that was already pushed back to give him eight days between starts -- before exiting the game early.

"There's been just a little stiffness," said Naturals manager Brian Poldberg after the game Wednesday. "We've given him a few extra days. We're not going to take any chances. He felt fine on his off-speed stuff, and his fastball, the velocity was still there, which is good. So we just got him out of there.

"It was planned he was going to go 75 pitches," continued Poldberg. "It was just one of those things where he said he was a little stiff, and we weren't going to take any chances."

Zimmer owned a 2.43 ERA and a 1.19 WHIP with 42 strikeouts and eight walks over 39 2/3 innings between the Rookie-level Arizona League and Class A Kane County in his pro debut last season. That campaign also ended prematurely when he underwent surgery to remove bone chips from his pitching elbow last August.