We've already determined that Jose Guillen's injury he suffered while running to first base this week isn't considered a big deal. Bob Dutton of the Kansas City Star recently laid out some details of the injury:
Royals calling Jose Guillen's injury a grade-one strain to the left quadriceps/hip flexor. Say he could play Friday after open date.
Today is Friday. The Royals play the White Sox tonight. We'll update this afternoon when the lineups come out.