Hernandez suffered the injury as he blocked the plate and tagged out Blue Jays first baseman Howie Clark, who was trying to score from first on a double by Reed Johnson. Clark slid into the catcher's knee, which which bent awkwardly.
Hernandez was helped off the field by trainer Todd Hutcheson and assistant trainer Jim Daniel. In the clubhouse after the game, he was walking on his own power and said there wasn't much pain.
"I knew it was going to be a bang-bang play, so I had to stay in there," Hernandez said.
He is batting .266 with seven homers and 25 RBI, and has thrown out 32 percent of potential base-stealers.