According to reports, Guillen had discoloration on an area near his right cheek while he expressed his displeasure with his club's recent play to media following the defeat.
"Nothing more painful than losing the game against Bruce Chen once again," Guillen told The Chicago Tribune. "That's more painful than this one."
The Royals tied the game at 1 in the eighth and picked up the winning run in the 11th inning on a wild pitch by Sergio Santos, which allowed Alex Gordon to score from third. Catcher A.J. Pierzynski appeared to have the low slider blocked, but it kicked away and Gordon hustled in to end the game.
"What I said in Detroit, I take it back," Guillen said after a second straight loss to the Royals. "This team is one day at a time: One day we're good, three days we're bad. We had no energy in the dugout. [Bad] approach at the plate, for the 90th time."