It's been a subpar season at the plate for Rolen, who is batting .242 in 65 games, with five home runs and 36 RBIs. He went on the 15-day disabled list for the second time on July 22, for what was originally listed as a strained left shoulder. The same injury had him on the DL from April 24 until May 12.
Rolen, 36, had two surgeries to repair a torn labrum in the same shoulder in 2005 while with the Cardinals, and he missed most of that season. He also had a minor procedure performed in 2007 by Kremchek.
Based on the diagnosis of an expected full recovery, Baker was optimistic that Rolen could return this season to contribute for the Reds down the stretch. He is making $6.5 million this season and is signed through the 2012 season for the same amount.
"I'm hoping whatever pain and what was wrong in there, they found. Hopefully, it won't return," Baker said of the latest surgery. "You hate to lose Scotty, but at the same time, we need him healthy in the present and future time, as well."
Without Rolen, the Reds are currently using utility infielder Miguel Cairo and rookie Todd Frazier at third base. Rookie Yonder Alonso, a left fielder and first baseman, started taking pregame ground balls at third base on Tuesday.
Top third-base prospect Juan Francisco has been recovering from his own injury -- a torn meniscus in his right knee that required surgery on July 8. Francisco was 5-for-10 on a rehab assignment with the AZL Reds in Goodyear, Ariz., and is expected to rejoin Triple-A Louisville on Thursday.
It is not yet known how long it would take for Francisco to be ready for a callup. He was on Louisville's DL in April when Rolen was out the first time this season, and missed his chance.
"It's bad timing for Francisco, because he was really next in line," Baker said. "He would have gotten a lot of playing opportunity had he not been hurt. Somebody else gets a break and opportunity to show what he can do."
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.