Dated June 12th on Detroit Tiger's MLB site:
Guillen out: Carlos Guillen said he'll probably be out until at least Thursday with a right hamstring spasm he suffered on Sunday.
"I don't think [Wednesday]," he said, "but maybe the day after."
The hamstring flared up Sunday when he mishandled a Carlos Delgado ground ball up the middle, but he said it had been bothering him for a couple days before that. He felt well enough to play through it, but the awkward stride he took trying to recover the ball set it off.
http://detroit.tigers.mlb.com/news/article.jsp?ymd=20070612&content_id=2021550&vkey=news_det&fext=.jsp&c_id=det