That's not how I remember it.
He was sprinting through a mine field, with no regard for his own life as he reached a burning building, which he then climbed up the side of (free hand), 25 stories to save a kid, broke through a window, grabbed the kid and then jumped out the window, grabbing another kid on a ledge on the 18th floor and then landed on top of a bed of rattlesnakes and then sprinted to safety. That's when he hurt his calf.
All the while, Anthony Rendon was watching, but looking like he didn't care. Joe Maddon was sipping a glass of wine and looked up and said, "that's cool, man."