Thanks to an outstanding defense in the second half and a decisive play by Justin Fields, the Pittsburgh Steelers remained undefeated on Sunday and took a 20-10 victory against the Los Angeles Chargers at Acrisure Stadium.

The defense did not allow the Chargers in the second half, held the visitors to minus-5 yards after halftime and has allowed just six points in three games this season, allowing the Steelers to overcome a 10-7 halftime deficit and improve their record to 3-0.

The Chargers, who had allowed the fewest points in the NFL entering the game, fell behind to 2-1.

Fields scored on a 5-yard run in the first half and created a 10-point lead in the second half when he threw a 55-yard touchdown pass to Calvin Austin with 7 minutes, 2 seconds left.

He is questionable because of a severe ankle sprain. Quarterback Justin Herbert started and led the Chargers to a three-point lead at halftime, but left the field with the score tied late in the third quarter and did not return.

The Steelers recorded all five sacks in the second half. They pressured reserve Taylor Heinecke, sacking him three times in the fourth quarter. Nick Herbig, who played in the first half because of Alex Highsmith’s groin injury, recorded two of the sacks.

It was the second time this season that the Steelers, who entered the game with the second-fewest points allowed in the league, did not allow a single point after halftime. They have yet to allow a touchdown in the second half and limited NFL rushing leader JK Dobbins to 44 yards on 15 carries.

Fields completed 25 of 32 passes for 245 yards, a touchdown and an interception, his first of the season. Herbert completed 12 of 18 passes for 125 yards and a touchdown before leaving the field.

Chris Boswell, who missed a 55-yard attempt late in the first half, scored from 35 yards on the first drive of the second half and the Steelers tied the score at 10-10.

Boswell’s 30-yard field goal with 14:14 left gave the Steelers their first lead on a drive in which the Steelers benefited from two personal fouls against the Chargers and a holding call that negated a third-down sack by Fields.

Heinecke’s first full series in Herbert’s place ended when he was sacked by TJ Watt for an 8-yard loss, forcing a punt. The Steelers then scored a touchdown on Fields’ 55-yard pass to Austin with 7:02 left to take a 20-10 lead.

Herbig and Cameron Heyward sacked Heinecke on the next drive, forcing a three-and-out. The Steelers played the remaining 4:59, getting the ball to the Chargers’ 1-yard line before Fields knelt twice and ran out the clock.

At halftime, the Chargers led 10-7.

Neither team managed a first down until their third possession. Both responded with a touchdown drive.

The Chargers were successful with Herbert’s 27-yard touchdown pass to Quentin Johnston, a play that left corner Joey Porter standing to focus on another receiver. Safety Minkah Fitzpatrick was late to help, and Johnston ran down the left sideline for a score.

The Steelers responded by driving 70 yards in 13 plays. Fields capped it off when he kept the ball on a third-and-3 play and scored on a 5-yard run. Fields faked the handoff to Jaylen Warren, dodged left and ran into the end zone, giving the Steelers their second touchdown of the season. The score was set up by Scotty Miller’s 20-yard pass reception.

The Chargers regained the lead when they capped a 12-play, 60-yard drive with a 28-yard field goal by Cameron Dicker with 3:13 left in the first half. This came after Herbert threw the first incomplete pass by either quarterback. Up until that point, he and Fields had combined to complete 19 of 19 passes for 159 yards.