COLORADO SPRINGS -- The Rockies are taking a new look at right-hander Jhoulys Chacin's ailing right shoulder in hopes of figuring out why he is not regaining the strength it takes to begin a throwing program, general manager Dan O'Dowd said on Thursday.

The Rockies expected Chacin to emerge as a rotation leader, but the 24-year-old last pitched on May 1, when he gave up 11 hits and seven runs in 4 2/3 innings during a 7-6 loss to the Dodgers, falling to 0-3 with a 7.30 ERA in five starts. The Rockies announced the next day they were optioning Chacin to Triple-A Colorado Springs, but the righty never reported. After an MRI exam revealed inflammation in the shoulder and biceps tendon, the club rescinded the option and placed Chacin on the disabled list.

Since then, Chacin has been limited to strengthening exercises but has not been allowed to throw. On Thursday, O'Dowd said that Chacin, who has been working with the Rockies' medical staff and head athletic trainer Keith Dugger, was being evaluated by an outside specialist.

"He's seeing another doctor today, which we'll report on once we get an idea of what that doctor has to say," said O'Dowd, who was in Colorado Springs to watch left-hander Drew Pomeranz, who was sent down to Triple-A to make corrections in his delivery. "We just can't figure out what's going on right now. [Dugger] and our medical people are very creative people. They're looking for answers."

Chacin has been a mystery for nearly a calendar year.

Through his first 15 starts last season, Chacin was 8-4 with a 2.71 ERA, and he was considered a candidate to pitch in the All-Star Game. But signs of trouble arose in the last of those 15 starts, last June 21, when Chacin walked six in 6 2/3 innings of a no-decision at Cleveland.

Since then, Chacin is 3-13 with a 5.14 ERA. The Rockies were hoping Chacin would reach his front-of-the-rotation potential this season. O'Dowd questioned Chacin's offseason conditioning during the winter, although manager Jim Tracy and pitching coach Bob Apodaca have said since then that the righty's conditioning wasn't an issue. During Spring Training, Chacin pitched through shoulder pain that never subsided, although he later admitted he didn't reveal the discomfort to the club, even when asked.

Chacin's was one of two key rotation injuries for the Rockies, who can lay significant blame on the starting rotation for their current 16-27 record, which has them in fourth place in the National League West, 13 1/2 games behind the first-place Dodgers.

Jeremy Guthrie missed three weeks with a right shoulder injury he suffered during a freak bicycle accident. Guthrie is back, although his work in two starts since his return has been inconsistent.

"Losing Guthrie and Chacin hurt," O'Dowd said. "We needed some core guys to stabilize things as these younger guys came along, and we had a freak injury, and now we have an injury we haven't gotten our arms around yet.

"I'm not trying to use that as an excuse because we should have other fallback options built in, but it's like two of them happened at the same time."