Los Angeles Chargers quarterback Justin Herbert exited Sunday’s 20-10 loss to the Pittsburgh Steelers after aggravating a high-ankle sprain that had already limited him in practice.

Herbert missed the entire fourth quarter as the Chargers (2-1) suffered their first defeat, while Pittsburgh (3-0) remained unbeaten with Justin Fields at the helm.

Herbert completed 12 of 18 passes for 125 yards, including a 27-yard touchdown to Quentin Johnston to start the game. However, Los Angeles’ offense stalled after a late first-half field goal, with the ground game contributing just 61 yards on 20 carries.

Midway through the third quarter, Herbert limped off the field following one of his two sacks, likely re-injuring the right ankle he hurt in Week 2 against the Carolina Panthers. He left the stadium in a walking boot.

Afterward, Chargers coach Jim Harbaugh explained that the team had intended to remove Herbert if he showed any signs of limping.