Chargers quarterback Justin Herbert is dealing with a high ankle sprain and is officially listed as questionable for Sunday’s game against the Pittsburgh Steelers.

The 26-year-old did not practice Friday on the campus of University of North Carolina-Charlotte after he was a limited participant Thursday. He had a thick layer of athletic tape wrapped over his right cleat on the field Friday as he worked with trainers on exercises off to the side.

Herbert, who suffered the injury last Sunday during a win over the Carolina Panthers, is “doing everything he can” to play Sunday, coach Jim Harbaugh said, but the quarterback could not commit to whether he expected to play.

“Thankfully it’s only Friday,” Herbert said, standing with most of his weight on his non-injured left foot.

Herbert said the pain is “not great, but it is what it is.” He is working around the clock with ice and compression to keep the swelling down. If he is unable to play, the Chargers would start Easton Stick or Taylor Heinicke.

Stick played in three preseason games with up-and-down results, which prompted the team to add Heinicke to the roster after training camp. Heinicke, a 10-year NFL veteran, has spent the last three weeks learning the complex scheme that at first had him tongue-tied while calling out a play. But Harbaugh and Herbert praised Heinicke’s ability to catch up quickly.

“I haven’t seen anybody get this up to speed as Taylor has,” Harbaugh said. “It’s been outstanding.”