Back spasms were the initial cause for his exit from Monday's game against Cleveland, but Guillen explained on Saturday that spasms are not the only ailment preventing his return to the lineup.
"One of my nerves [in my back] is inflamed," Guillen said. "So I have to wait until the inflammation goes down."
Guillen missed three games earlier this month with a pinched nerve in his back, so back troubles aren't a new occurence. This time, though, the injury has forced the infielder to miss nearly a week of action.
And Guillen can't pinpoint any date for a return.
"I don't know," Guillen said. "It could take a while. A week? I don't know."
Guillen has been diligently applying ice to his back, one of the few tried-and-true methods for keeping inflammation down. Because rosters expand on Monday, a trip to the disabled list seems unlikely.
The two-time All-Star is hitting .286 this season with a .376 on-base percentage and 10 home runs. The Tigers have gone 10-11 in the 21 games that Guillen has not appeared, including a 1-3 mark since he left Monday's game.
David Just is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.