It's an injury more likely caused over time than by one incident, such as the slide into Guillen's knee from Yankees outfielder Brett Gardner that ended Guillen's season last month. It's a significant enough surgery that it puts at least some question into Guillen's readiness for the start of next season.
The timetable suggests Guillen will not be able to put weight on his leg for 6-8 weeks, and he won't be able to pick up significant physical activity for four months. That would put him on track for light running in January. The timetable to get him back to baseball activity is more likely around 4-5 months, Rand said, which would be right around the early part of Spring Training.
"The time frame [for a return to game action] usually on these things is in and around the six-month mark," Rand said. "Obviously, it kind of puts into question him being ready to begin the season."
With so little case history among baseball players, it's hard to tell. Microfracture surgery is more common in basketball, having been performed on such players as Tracy McGrady and Chris Webber. Success hasn't been guaranteed, but the results have improved as the surgery has become a little more common.
"Microfracture surgery, in and of itself, that makes it obviously a longer time period [for recovery]," Rand said.
Fellow Tiger Clete Thomas had the same surgery this summer.
Dr. Michael Warren, who originally examined Guillen in New York after Gardner's slide, performed the surgery. He specializes in knee and shoulder injuries and serves as the team physician for the NFL's New York Giants.
Like others, he suspected something more than a bruise when Guillen's knee showed little progress after three weeks of rest, usually the maximum time for a bone bruise to heal. At the very least, they wanted to take another look while there was still time for recovery to get him ready for next season.
What they found, obviously, wasn't encouraging. Rand compared the injury to a divot on a golf ball. It wasn't a fracture, but the surgery itself involves a microfracture to try to trigger the healing process. Guillen has had knee problems in the past, including surgery to repair a torn anterior cruciate ligament in his right knee in 1999 and 2004.
Until this summer, the Tigers had avoided Guillen in the infield the past couple of years to avoid wear and tear. However, he said he felt more comfortable playing as an infielder than in left field, mainly because he could keep moving and keep his legs fresh. Second base was his fifth different position since 2007.
What it means for Guillen and the Tigers next season is a lot of uncertainty. Even if Guillen didn't have additional surgery and was ready to start next season, the Tigers appeared prepared to go into 2011 with options. Team president/general manager Dave Dombrowski told WDFN last week, "I feel comfortable going into next year at second base with what we have at this point with [Will] Rhymes and [Scott] Sizemore."
Manager Jim Leyland said Sizemore will get playing time at second base over these final two-plus weeks to the season, starting against left-handed pitchers. It isn't difficult to envision a timeshare at second next season, with Guillen also playing there when he's ready while potentially shifting to other spots on occasion.
Before the Tigers can decide where to play Guillen, however, he has to be able to play. That will be the focus of the offseason.