San Diego Chargers tight end Antonio Gates left Sunday's 20-17 loss to the St. Louis with a left ankle injury.
He will undergo an X-ray and an MRI on Monday in San Diego.
Gates injured his left ankle in the second quarter. He came back on the field for a series before he was taken to the locker room late in the first half. He was not on the sideline for the second half.
Gates got hurt blocking on a carry by running back Ryan Mathews.
"I got tripped up and I guess some guys fell on the back of my leg," said Gates, who was wearing a walking cast in the locker room. "That's initially how it started. Then on a pass down the middle on the last play I was in, someone fell on my ankle. I just couldn't go. I couldn't move."
San Diego coach Norv Turner said he is unaware of how seriously Gates is hurt.