OAKLAND, Calif. -- After returning from a rib injury to orchestrate a late fourth-quarter touchdown drive, Pittsburgh Steelers quarterback Ben Roethlisberger said he assumes he'll be available for the Week 15 clash with the New England Patriots.

But perhaps Roethlisberger could have prevented the 24-21 loss to the Raiders if he were on the field sooner. Roethlisberger, who left the field before halftime and didn't return until 5 minutes, 20 seconds were left in the fourth quarter, said he was waiting for coach Mike Tomlin to "tell me when to go" back into action.

Tomlin explained why he waited to give that green light.

"He got looked at at halftime. He got treatment, he came back out," Tomlin said of his quarterback. "We were waiting to see if he was gonna be able to come back in. He was. He probably could've come in a series or so sooner, but we were in the rhythm and flow of the game. He was ready to go when he got back out there."

Roethlisberger left the Oakland-Alameda County Stadium field with 10 seconds left in the second quarter after a 1-yard touchdown pass to JuJu Smith-Schuster gave Pittsburgh a 14-10 lead. Backup Josh Dobbs started the second half, and Roethlisberger emerged from the tunnel early in the third quarter only to watch from the sidelines.

But after the Steelers lost the lead, Roethlisberger returned and promptly restored it by driving the offense 75 yards downfield with another 1-yard touchdown to Smith-Schuster. The Raiders countered with quarterback Derek Carr's 6-yard touchdown pass to Derek Carrier with 25 seconds left.

The Steelers' hook-and-ladder play for 43 yards set up a last-second field goal attempt from 40 yards that Chris Boswell missed as he slipped on the grass.

Earlier in the game, Roethlisberger took a sack and another shot from the Raiders' defense. On one second-down throw in the red zone, Roethlisberger stayed down for a few seconds after a hit.

The quarterback deferred to Tomlin on details of his injury.

"You're asking how I feel during a football game where I'm getting beat up," said Roethlisberger, who finished 25-of-29 passing for 282 yards and two touchdowns. "So, I felt OK."

The Steelers' offense struggled without him. Dobbs completed 4 of 9 passes for 24 yards and an interception in four series of work. The running game never came alive in the absence of the injured James Conner, recording 40 yards on 19 carries.

Despite knee injuries in 2015 and 2016, Roethlisberger has been largely healthy the past two seasons.

But he has work to do to extend his playoff streak to a fifth consecutive season. A three-game losing streak leaves Pittsburgh at 7-5-1, a half-game ahead of the Baltimore Ravens in the AFC North.

"We all need to look in the mirror and figure out what's going on," he said. "It starts with each individual. We need to look inside first."