MIAMI -- An MRI and exam by Cardinals team doctor George Paletta late Tuesday indicated that right-hander Chris Carpenter has apparently escaped serious injury, but he still will miss his scheduled Friday start in Cincinnati.

Paletta confirmed that Carpenter has a muscle strain in his right "posterior shoulder," according to a press release issued by the Cardinals. Paletta indicated that Carpenter has no rotator cuff problem and will rejoin the team in Florida for more medical treatment.

Carpenter caught a 2 p.m. CT flight to St. Louis on Tuesday to have Paletta make a diagnosis. He had injured the shoulder pitching against the Cubs on Sunday.

At Dolphin Stadium, the Cardinals had already been considering their options to fill in for Carpenter on Friday.

Manager Tony La Russa had said, "If I have any doubts about his health, I'll err on the side of caution."

Pitching coach Dave Duncan said any replacement for Carpenter would come from among his bullpen. He mentioned Brad Thompson and Jaime Garcia, who both have starting experience.

It is still difficult to pick a likely choice between the two because La Russa emphasized before Tuesday night's loss to the Marlins, "We need to win the next three games any way we can."

In other words, he'll use as many pitchers to win a game as is necessary. That puts both Thompson and Garcia in line to be used as relievers before Friday, when the Cardinals open a series at Cincinnati.

Neither Thompson nor Garcia pitched on Tuesday.

Of Thompson's 19 appearances this season, three have been starts. He is 4-2 with a 4.34 ERA. Garcia has six appearances, with one start. He is 1-1 with a 3.27 ERA.

Garcia has pitched only 11 innings for the Cardinals, while Thompson has thrown 45 2/3.

At least the Cardinals can take solace in the fact that Carpenter is not lost for the season. The pitcher acknowledged Monday that the area was still "a little sore." He said it's the first time he's been injured there.