Cuthbert slid with a forearm and elbow into the left thigh of Perez, who called off Chien-Ming Wang (3-0), settled under Adam Eaton's foul popup about 30 feet from the plate near the third-base line, and snagged the ball just before he was hit.
Perez was taken for an MRI after the game, and the extent of his injury was not announced. The preliminary diagnosis was a bruised left thigh.
On Sunday, the Royals announced that they recalled catcher Tony Cruz from the Triple-A Omaha Storm Chasers for the game against the White Sox.
The Royals rallied for seven runs in the bottom of the ninth to escape with an8-7win.They became just the fifth team since 2010 (5-2,810) to win when trailing by six runs entering the bottom of the ninth.
But the health of Perez was at the forefront afterward.
"Now it's a waiting game,'' Eric Hosmer said. "We won the game today, but that will be the more important win if we find out nothing serious with him happened. Salvy is our guy. He's the leader of this team. He's an All-Star. He's everything. When you see a guy like that goes down, it fires you up. You want to pick up the pace cause you've got to pick him up.''
Perez immediately raised his right arm, signaling for assistance. Two minutes later, Perez hobbled off the field with his arms draped over the shoulders of manager Ned Yost and head athletic trainer Nick Kenney.
"The good thing about it, at least as far as we could tell, there was no structural damage to his knee,'' Yost said. "So, that was what I was worried about. He sustained a pretty good quad contusion [and] Cheslor suffered a mild quad contusion, when they hit.''
It's been a tough week for the Royals when it comes to collisions and injuries.
Royals third baseman Mike Moustakas and left fielder Alex Gordon collided last Sunday while chasing a foul ball at Chicago, and both landed on the disabled list. Gordon has a broken right wrist and is out for three to four weeks, while Moustakas tore the ACL in his right knee and is likely out for the season.
"That wouldn't have happened with Moose, because they've played together so long,'' Yost said of Saturday's collision involving Moustakas' replacement, Cuthbert. "Moose knows what Salvy's capabilities are, and Ches just put his head down and came hard."
Information from The Associated Press was used in this report.
Perez leaves game with quad contusion after collision
Royals catcher Salvador Perez is helped off the field after colliding with teammate Cheslor Cuthbert while fielding a pop up and suffering a quad contusion on the play.