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"He came in [Sunday] with a little soreness in his knee," Mattingly said. "At that point, we were like, 'OK, I'm not taking him tomorrow.' "
Stanton had surgery on the same knee in July 2012.
The Marlins are hopeful the knee just needs a few days of rest. But as a precaution, Stanton was examined on Monday by team physician Dr. Lee Kaplan.
"We actually had him go see Kaplan, just to be sure," president of baseball operations Michael Hill said. "Obviously, he's a big part of our team, a big part of our lineup. We want to make sure everything is good. Right now, it's just soreness and rest, and we'll see how he reports [Tuesday]."
Right now, it's just day to day, and no MRI has been scheduled. The 26-year-old slugger has appeared in two Grapefruit League games, going 1-for-3 with a double and a walk.
As for when Stanton will be ready for game action, the Miami manager said: "We'll just see. The one thing we'll be is cautious. We've got time right now. I'm not really worried about [him]."
Stanton broke his left hamate last June and appeared in 74 games in 2015.
Early in Spring Training, a number of players are dealing with soreness.
"You'd rather take a couple of days and get that right," Mattingly said.
The fact Stanton has missed so much time due to injuries in his career raises concerns.
"I understand," Mattingly said. "At this point, I'm not going to be too concerned, but I guess, obviously, you pay attention. It's sore for a reason. We're not sure what that is."
The Marlins were starting Jose Fernandez on Monday. Until Stanton was scratched from the trip, it would have been the first time the outfielder and Fernandez were in the lineup together since May 9, 2014.