MESA, Ariz. -- Rockies rotation candidate Eddie Butler left Monday's 11-2 loss to the A's with right shoulder fatigue, and he was scheduled to be evaluated later in the afternoon.
Butler, MLB.com's No. 2 Rockies prospect, was in the middle of an impressive spring. He entered Monday's start with a 2.63 ERA in four Cactus League outings (two starts), and he had a chance to further impress with another good outing.
That, however, never materialized.
Butler allowed two hits -- both ground balls -- but he never seemed comfortable, issuing a pair of two-out walks to load the bases. He got out of the jam with a hard-hit flyout to right field by Oakland's Stephen Vogt.
Righty Scott Oberg replaced Butler in the bottom of the second.
Rockies manager Walt Weiss said after the game he didn't have any update.
"That's all I know. I haven't even talked to him yet," Weiss said. "He came out, went up in the training room. It sounds like it's better than it looked like so we're hopeful he'll be fine."
Weiss said Monday morning that it wasn't too much of a stretch to think of Monday's outing as an audition for Butler.
"Guys that are coming in and competing for a spot, it's important that they perform," Weiss said. "The guys you don't pay a whole lot of attention to ... are the guys that had a spot before camp started. But the other guys are fighting for a spot, trying to make an impression. That performance is important."
That rotation spot is now on the back burner as the Rockies hope for the best for their young prospect.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.