Manager Trey Hillman said that Gordon has a torn muscle in his right leg. In a major move, outfielder Mark Teahen returned to third base for Friday night's game against the Detroit Tigers.
Also on Friday, the Royals placed left-handed pitcher Ron Mahay on the disabled list and recalled right-hander Kyle Davies from Triple-A Omaha to start Saturday night's game against the Tigers.
That move was no surprise. Mahay has an ailment of the left foot and has pitched just once in the last 12 games. His stay on the 15-day disabled list was backdated to Aug. 16.
Gordon came out of Thursday's game in Cleveland after the fourth inning. He suffered a pull in his right leg while charging in to field a roller. There was no immediate estimate of how long he might be sidelined.
"It's a torn muscle so I'm sure it's not going to be a matter of days, it's probably a matter of weeks," Hillman said.
Although Gordon indicated after the game that he did not consider the injury serious, a subsequent examination proved otherwise.
"He's got a tear in the upper right side of his leg, the groin region. It's actually a deep hip flexor muscle. We're just getting the results back," Hillman said.
Hillman was not surprised when he heard the extent of Gordon's injury.
"No, not with the amount of pain that he was in," Hillman said. "He came off the field very tenderly and actually wanted to go ahead and have his next at-bat but, being in that region, I told him to go in and get it checked.
"We shut him down and I'm glad we did, obviously, because it is a tear."
Gordon was batting .254 with 14 home runs and 51 RBIs in 122 games. He'd missed Tuesday's game in Cleveland because of a stiff back.
Teahen played at third base in a regular-season game for the first time since 2006, when he was the Royals' starter at that position. He switched to right field in Spring Training 2007 to make room for Gordon at third.
"Hopefully, it's like riding a bike," Teahen said. "I grew up playing there so I'm not too worried about it. I'm going to have some fun with it."
Teahen played third base briefly in Spring Training this year. Just on a whim, he took some ground balls at third during pregame practice the day before Gordon was injured.
"I'm going to try to remember what I used to do and, hopefully, Gordon's not out for too long," he said.
Mahay is suffering from plantar fasciitis, an inflammation of the foot that causes pain in the heel. He'd had the problem for some time and the Royals revealed it on Aug. 8.
In his only appearance since then, a week ago at Yankee Stadium, he faced three batters. He retired one, walked the other two and was charged with two runs that resulted in a 4-3 loss to the Yankees.
However, the Royals have missed Mahay in the back end of the bullpen. He'd developed as an effective setup man for closer Joakim Soria and had a 5-0 record with a 2.91 ERA.
Davies will return to the rotation on Saturday, after being optioned to Omaha last Friday. He missed just one start with the Royals and pitched only one inning for Omaha. He has a 5-4 record with a4.71 ERA in 14 starts.
It's been a rough period for injuries for the Royals. Pitcher Luke Hochevar went on the disabled list on Wednesday with a rib-cage contusion and outfielder Mitch Maier went on the DL on Thursday after being hit in the face by a pitch.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.