The Bears valiantly rallied from a 20-6 deficit entering the fourth quarter with three touchdowns Monday night, ultimately taking a 27-26 lead over the stunned Steelers on Justin Fields' 16-yard touchdown pass to Darnell Mooney with 1:46 remaining.

But quarterback Ben Roethlisberger followed by calmly directing a 7-play, 52-yard drive to set up Chris Boswell's 40-yard field goal with just :26 to play, giving the Steelers a 29-27 victory at Heinz Field.

With no timeouts remaining, the Bears advanced to the Steelers' 47 with :02 to play. But Cairo Santos' 65-yard field goal attempt fell well short as time expired.

The Bears outgained the Steelers 414-280 but were plagued by penalties, drawing 12 flags for 115 yards. Two of the costliest penalties had to be addressed by referee Tony Corrente via a pool reporter after the game because they were controversial, one that nullified a touchdown and another that extended a Pittsburgh drive late in the game.

Fields completed 17 of 29 passes for a career-high 291 yards with one TD, one interception and an 89.9 passer rating, and rushed for 45 yards on eight carries. David Montgomery rushed for 63 yards on 13 carries and Khalil Herbert added 13 yards on four attempts.

Cole Kmet led the Bears with six catches for a career-high 87 yards. Allen Robinson II added four receptions for 68 yards. Mooney caught three passes for 41 yards. And Marquise Goodwin had one 50-yard reception.

The Bears defense played well most of the game, with the exception of the Steelers' first and final possessions.

The Bears fell to 3-6, losing their fourth straight game.

"The only way to get rid of that sting is to win," said coach Matt Nagy. "Unfortunately, it's never fun going into a bye on a loss. Now, you've got to self-evaluate, self-reflect, and that's what the guys talked about in the locker room … The guys fought. You've got to give them credit for that, but in the end, not enough credit because we didn't win."

Here's what transpired in Monday night's game:

First half

After the Bears opened the game by going three-and-out, the Steelers took a 7-0 lead on their first possession on rookie running back Najee Harris' 10-yard touchdown run.

The TD capped a 6-play, 59-yard drive that was highlighted by Roethlisberger's 26-yard pass to Chase Claypool on third-and-7 from the Pittsburgh 49. Beating a blitz, Roethlisberger lofted the ball down the right sideline to the 6-4 Claypool, who leaped over 5-11 cornerback Kindle Vildor to snag the pass.

The Steelers extended their lead to 14-0 on Roethlisberger's 4-yard touchdown pass to tight end Pat Freiermuth on third-and-goal early in the second quarter. The Bears' coverage was initially good, but no pass rush enabled Freiermuth to get open.

Pittsburgh started the drive at the Bears' 36 after defensive end Cam Heyward blocked a Fields pass at the line of scrimmage and somehow intercepted the ball.

The Bears eventually cut the deficit to 14-3 on Santos' 30-yard field goal with :15 left in the half. They settled for the field goal after Fields failed to connect with Jimmy Graham in the end zone on back-to-back plays from the 7—and after a false start on Larry Borom—from the 12.

The Bears struggled on offense before the field-goal drive, with their first five possessions resulting in four punts and one interception. In the first quarter, they had trouble lining up for a play and were forced to call a timeout. On the next play, they were penalized for being in an illegal formation.

Penalties in the first half nullified Fields' completions of 16 yards to Robinson and 17 yards to Jakeem Grant Sr..

Second half

The Bears closed the gap to 14-6 on Santos' 22-yard field goal on their first possession of the second half. The kick came after a penalty erased Fields' apparent 1-yard TD pass to Graham. James Daniels was flagged for a low block on T.J. Watt, but it appeared that Daniels barely touched Watt.

Fields put the Bears in position to score with a 50-yard completion to Goodwin to the Steelers' 14.

The Steelers answered with a 9-play, 75-yard drive capped by Roethlisberger's 10-yard TD pass Freiermuth with 2:08 left in third quarter. Boswell missed the extra point, keeping the score at 20-6.

The Bears responded with a 6-play, 82-yard drive of their own that culminated in Mooney's 15-yard touchdown run, closing the gap to 20-13. Lining up in the Wildcat formation, Montgomery took the shotgun snap and handed off to Mooney. The key play on the drive was Fields' 28-yard pass to Graham down the seam.

Boswell followed with a 54-yard field goal that restored the Steelers' two-score lead at 23-13 early in the fourth quarter.

Grant then fumbled at the conclusion of a 32-yard kickoff return when he was hit by Steelers cornerback James Pierre, and Boswell recovered the loose ball at the Bears' 42. But the defense held, forcing Pittsburgh to punt.

The Bears then cut the deficit to 23-20 as Joel Iyiegbuniwe forced Ray-Ray McCloud to fumble on a punt return, and DeAndre Houston-Carson picked it up and returned it 25 yards for a TD with 6:31 remaining.

Elevated from the practice squad earlier in the day, outside linebacker Cassius Marsh sacked Roethlisberger on third down. But Marsh was flagged 15 yards for taunting, giving Pittsburgh a first down. Boswell's 52-yard field goal eventually widened the margin to 26-20 with 2:52 left.

Marsh celebrated the sack with a whirling kick and then took a few steps toward the Steelers bench, but he was still in the middle of the field. Corrente defended the controversial call, telling a pool reporter after the game: "First of all, keep in mind that taunting is a point of emphasis this year. And with that said, I saw the player, after he made a big play, run toward the bench area of the Pittsburgh Steelers and posture in such a way that I felt he was taunting them."