Guillen said he aggravated his groin while delivering an RBI single in the fifth. That hit made it 2-2, and it stayed tied until the eighth. Upton's ball fell beyond second baseman Mark Grudzielanek and well in front of Guillen. With runners on second and third, reliever Horacio Ramirez surrendered the Crawford triple.
"I should have been smart and just taken myself out of the game right there," Guillen said, thinking back to the fifth. "I could not even walk. I just tried to be in the game and tried to make it better. But I just think it got worse.
"It was one of those situations where you really try to stay in the game. ... You care about winning."
Guillen had let Grudzielanek and center fielder David DeJesus know that he would need some help defensively after hurting his groin. Grudzielanek aggressively went after Upton's popup before looking up to see if Guillen was taking charge. Guillen wasn't.
"The fans got upset," Guillen said. "I hear all kinds of stuff. I should have caught that ball, but I'm just having a problem coming in."
Guillen termed his pulled groin "real serious." Had the Royals taken the lead, Guillen said he likely would have come out for a defensive replacement.
Asked whether he would be able to play on Sunday, Guillen said: "I don't think so. We'll just leave it up to [manager Trey Hillman], whatever he wants to do. But I don't think I'll be able to play in the field. We'll see where we're at tomorrow and go from there."
Hillman was ejected from Saturday's game in the fourth inning after arguing that Alex Gordon had beaten a play at first. The Royals rallied from an early 2-0 deficit, waited out a one-hour, 13-minute rain delay and, even after Upton's popup fell, had a chance to escape the eighth inning unscathed. Prior to his triple, Crawford sliced a foul ball down the left-field line and the ball just ticked off Esteban German's glove as he raced toward the stands.
Finally, Crawford solved Ramirez, who was trying to come inside to Crawford but missed his spot.
"It caught too much of the plate and he's a good hitter," Ramirez said. "He got good wood on it. My job is to make pitches and pick guys up sometimes. For me, it's a little frustrating that I wasn't able to do that today."
Carlos Pena's homer in the ninth made it a three-run cushion for closer Troy Percival. The Royals used a Ross Gload triple and a German single to close within two, at 5-3, but Percival steadied himself and picked up his 22nd save.
And after the Royals' fifth loss in their first six games of the homestand, Guillen was left to treat his groin and mull his decision to stay in the game.
"To lose a game like that, it's tough," Guillen said.