Carlos Silva (AP)

FORT MYERS, Fla. — When the Red Sox had Carlos Silva work out for them in December, they were impressed by his stuff, which seemed to have greater life than at any point in years. However, mindful that he hadn’t pitched in the majors since 2010, they were comfortable signing him only to a minor league deal.

While the right-handed sinkerballer had been slated to compete for a rotation spot this spring, that prospect is no longer realistic. The 32-year-old has been shut down indefinitely due to right shoulder inflammation. He is no longer being considered for the rotation, and it remains to be determined what his shoulder will allow him to do.

“That’s probably going to set him back enough that he won’t be totally in the mix,” said Sox manager Bobby Valentine, who said that while a definitive timetable was unavailable, the injury will keep Silva out of the “little picture situation.”

Valentine said that the issue was related to a pre-existing condition that the Sox knew about.

“I think we know exactly what it is and we were hoping it wouldn’t present itself as quickly as it did,” said Valentine.

Asked what the longer-term implications were of the condition, Valentine said simply, “It’s being discussed.”

Silva, 32, last pitched in the majors in 2010 with the Cubs, when he went 10-6 with a 4.22 ERA. He was 2-1 with a 3.52 ERA with the Yankees’ Triple-A team last year before getting released.

With Silva out of the mix, the pitchers in camp who remain in the mix for one of the last two spots in the Sox rotation are Daniel Bard, Alfredo Aceves, Andrew Miller, Vicente Padilla, Felix Doubront and perhaps Aaron Cook, though Cook has been brought along on a slower schedule than his colleagues as a precaution in light of his shoulder injuries in recent years.

OTHER NOTES

– Aceves will make his second appearance of the spring. Valentine suggested that the right-hander’s versatility presents something of a managerial conundrum, as the team will be challenged to figure out where he provides the most value. Aceves will continue to be evaluated as both a starting and bullpen option.

“It depends on everybody else he’s involved with, what piece he is in the puzzle. It can be a little corner piece, and end piece or that last piece that was so hard to find. I’m not sure yet,” said Valentine. “He’s almost a pitching savant kind of guy. He seems to have a great feel for his craft. Innate, almost. He sees things other guys don’t see, I think.”

– Valentine suggested that with Carl Crawford likely to open the year on the DL and the Sox in a position (potentially) where they won’t need a fifth starter on the roster until the fifth or sixth game of the year, the team could open the year with the equivalent of a 26- or 27-man roster.

– During spring training, the Red Sox will evaluate Junichi Tazawa solely as a reliever. Valentine left the door open for the club to stretch him out after spring training, but for now, it appears the Sox are considering him as a relief option.

“If it comes to a time where we decide his absolute future is as a starter, it probably won’t be during these 33 days,” said Valentine.