The injury happened in the top of the third inning after Ventura singled to right, his second Major League hit. Alex Gordon followed with a grounder to second, and Ventura danced out of the baseline trying to avoid the tag. He came back to the dugout limping.
Ventura started the third inning, got two outs, but then gave up a long homer to Cody Asche.
"They taped him up and he thought he could give it a shot," Yost said. "The first hitter, it was OK. But then it got progressively worst.
"When he got to 3-2 on the last hitter, I knew I would go get him because he was starting to limp pretty badly."
Ventura didn't seem overly concerned about the injury after the game.
"It feels better right now than it did when they took me out of the ballgame," Ventura said through interpreter Pedro Grifol. "It's still a little swollen, but the swelling is getting a little better. I'm going to continue to work to see if I can get better.
"Right now, it's too early to tell about the next start. I'm going to have to wait a couple days to see how it feels."
Ventura agreed with the decision to come out of the game.
"It got to a point where it was starting to get worse," Ventura said. "Ned made the decision to take me out of the ballgame before it got any worse."
Before the injury, Ventura already had given up a three-run homer in the first to Phillies catcher Cameron Rupp.
"I wanted to locate a fastball on the outside part of the plate and it stayed up," Ventura said. "He made good contact, home run."
After two straight outstanding starts before serving an eight-game suspension, Ventura now has given up 11 runs in his last two starts over eight innings.
"I was in good rhythm and maybe the extra days that I was suspended kind of threw my rhythm off a little bit," Ventura said. "But again, I'm going to continue to work to see if I can get back into that rhythm I was in."
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. This story was not subject to the approval of Major League Baseball or its clubs.