Casas suffered the injury when he hit first base awkwardly trying to beat out an infield single in the second inning. He hit the bag and immediately crumbled to the ground, grabbing his left knee. Casas had to be carted off the field. Here's the play:

The one thing the Red Sox know about their situation at first base is that Triston Casas won’t play for the rest of the season. Casas ruptured his left patellar tendon on Friday and will soon have surgery that will require an extensive rehab.