PITTSBURGH (AP) — The Denver Broncos' perfect September is gone, replaced by the reality of October.

Two weeks, two losses to playoff teams a year ago, the latest a 27-19 setback in Pittsburgh on Sunday. The Broncos (3-2) were pushed around for three quarters before an improbable late rally gave them a chance to tie the game in the final seconds.

Teddy Bridgewater's fourth-down heave in the back of the end zone to Courtland Sutton wound up in the hands of Pittsburgh defensive back James Pierre instead. That sealed a defeat that will do little to quiet skepticism that Denver's 3-0 start was more of a product of who it played, not how it played.

“If we want to be where we want to be we can’t start off slow,” running back Melvin Gordon said. “We can’t wait until we get in a hole and then come together as a unit and try to pull it together at the end. This is the National Football League. It’s too hard.”

Especially on the road. Especially against a team that came in with a palpable feeling of desperation while riding a three-game losing streak. The Steelers (2-3) and the NFL's worst rushing offense piled up 147 yards against Broncos outside linebacker Von Miller and a defense that showed little of the edge that seemed to come so easily during wins over Jacksonville and both New York teams.

Of course, the Jaguars, Jets and Giants are rebuilding. Baltimore, which whipped Denver 23-7 last weekend, and the Steelers are not. Both are built to win now. Presented with an opportunity to prove they are, too, the Broncos instead showed how much work remains.

Three times Denver defenders had a potential interception smack off their hands to the Heinz Field turf. A poorly timed spike by running back Javonte Williams following a 49-yard run in the second quarter was followed by a sack that forced the Broncos to settle for a field goal.

A 17-yard pass interference flag on cornerback Kyle Fuller set up a 1-yard touchdown dive by Pittsburgh's Najee Harris. A leverage penalty on defensive end Dre'Mon Jones on a Steelers field goal attempt in the third quarter instead gave Pittsburgh a first down.

Three plays later, Chase Claypool hauled in an 18-yard touchdown pass late in the third quarter that put the Broncos in an 18-point hole.

Only then did Bridgewater, who spent most of the week in the NFL's concussion protocol, and the offense spring to life. Denver rolled up 215 of its 374 yards in the fourth quarter, putting together three long drives that gave them an outside shot to force overtime.

It was fast. It was furious. And it was futile.

“We just have to have some energy (earlier in games)” Bridgewater said. “We might need to do like the colleges and do goal-line in pregame or something … just bash heads or something, just to get the blood flowing.”

That would require hitting something hard, something Denver's defense failed to do against Pittsburgh's retooled offensive line. While their lone sack on Ben Roethlisberger did produce a turnover, it was just one of two plays in which the Broncos managed to get their hands on the 39-year-old quarterback.

Miller, who came in with 4 1/2 sacks through four games, had just two tackles and was no match for Claypool when he found the 6-foot-5 wide receiver lined up in the slot in the second quarter. That turned into a 59-yard gain.

“I let him get inside and he’ll run all day,” Miller said.

Claypool did. So did Harris. The rookie became the first Steelers running back to top 100 yards in nearly a year against a defense that came in second in the NFL in points allowed and fifth against the run.

“He's a runner," Broncos coach Vic Fangio said of Harris. “They’ve been committed to the run. They blocked us good. He ran good. He’s a good runner. We didn’t play it well enough.”

Another test awaits next week at home against rival Las Vegas. Both squads find themselves trying to keep pace in a loaded AFC West. If the Broncos are to prove their early success wasn't a mirage, time is running out.

“I’ve been in positions worse than this and came out 12-4,” Gordon said. “I’m not bothered by being 3-2. It’s 3-2. There’s a lot of football left. You can’t get down.”

Especially by 18.

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James Pierre

Another slow start dooms Broncos in loss to Steelers