Guillen, whose shoulder landed him on the disabled list May 5, visited with specialist Dr. David Altchek for a second opinion and an MRI exam last Friday after his rehab progress halted. The result is no change from the current track, according to head athletic trainer Kevin Rand.
Rand referred to it as a throwing shoulder, the product of years of play at shortstop.
"He basically shows the wear and tear of playing this game for a long time," Rand said.
Whether it's a condition that can eventually be reversed or will instead bother Guillen to some degree for the rest of his career is unclear. The main goal for the Tigers is to get him free of pain, then back doing baseball activities.
Guillen is in his 12th Major League season. He spent the first 11 of those as an infielder -- initially at third base in Seattle, then at shortstop -- before the Tigers converted him back to third base last year and then to left field this season.
Considering Detroit's 10-day road trip earlier this month proved to not be enough time for Guillen to get pain-free, Rand said the team has no timetable for getting him back on the field. His first task once he's cleared to resume baseball activity is to start throwing again.
"Just take it as it comes," Rand said.
Guillen accompanied the team on this road trip, but hasn't been able to take batting practice. He tried swinging off a tee last week but is still battling pain in the shoulder. At this point, Guillen's left to do more general workouts.
The Tigers have done well over the two weeks Guillen has been out, thanks mainly to contributions from young outfielders Clete Thomas and Josh Anderson. But as manager Jim Leyland pointed out Monday, getting veteran hitters such as Guillen going is crucial to the Tigers' fortunes over the course of this season.
The shoulder problem and a sore Achilles tendon that flared up during the Tigers' season-opening series at Toronto have limited the 33-year-old Guillen to 24 games, just 12 of them in the field. He owns a .200 batting average (18-for-90) with four doubles, no home runs, six RBIs and 15 strikeouts. His 113 games played last season marked the lowest total of his five years with the Tigers, having missed the final 31 games with lower back spasms.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.