Momentum is a fickle construct. An offense can spin from looking lifeless, gasping for any positive pickup that might keep fans in purple from sinking further into their seats, to suddenly sharp and decisive, impelled by the defense landing a punch right on the jaw.

It has been a savior for the Ravens twice already this season. It happened again Saturday night (twice) in exorcising their Pittsburgh Steelers demons, 34-17. And it’s proved that Baltimore’s defense can win a rock fight.

“Our offense has bailed us out so many times,” cornerback Marlon Humphrey said. “It felt good to be able to return that favor.”

Baltimore’s offense opened the second quarter looking completely disjointed with a short-lived drive that included two penalties (one declined) followed by a shanked, 14-yard punt by Jordan Stout.

Then four plays moved the Steelers just outside the red zone with a chance to take their first lead. From the 23-yard line, Russell Wilson took off between the hashes, only green grass in front of him, appearing destined for the end zone.

Kyle Van Noy called it an “Oh, [crap]” play, admitting he lost track of containing the Steelers quarterback. Safety Ar’Darius Washington cut back and put his shoulder into Wilson’s waist. The ball popped loose short of the goal line and Van Noy crashed down to recover it.

The Ravens responded to the tune of an eight-play, 96-yard scoring drive, capped by a go-ahead 14-yard touchdown pass from Lamar Jackson to Rashod Bateman. A drive that more closely resembled the NFL’s best offense by most metrics after what Humphrey called “the biggest play of the game.”

“We preach about it all the time,” Washington said. “The DBs, we bring the energy. If we’re on point, the whole defense is on point. Then it carries over, if the offense is struggling, we can get those guys going too.”

That wouldn’t be enough to fully escape their divisional rival. Pittsburgh had previously bested Baltimore in eight of their past nine meetings. These games always swing back and forth. It would take more than one to get the monkey off their back.

Up a touchdown in the fourth quarter, the Ravens took over possession near midfield. Derrick Henry turned and burned the first play 44 yards up the sideline. Then Lamar Jackson threw an uncharacteristic interception — only his fourth of the year. It was like twisting the knife in the belly of any Baltimore momentum. The stadium fell solemn.

But the defensive back room, as Washington said, prides itself on being the ones to help negate such gaffes. As was the case when Humphrey intercepted Wilson and trotted into the end zone for his first career pick-six.

Wide receiver Zay Flowers sang a colorful response: “I said ‘backpack, backpack.’ You know the little ‘Dora [the Explorer’] song? Just telling them to pack it up.”

It put Baltimore (10-5) up two scores and, as far as momentum goes, was enough to cement the win this team had longed for, helping clinch a playoff berth and giving them a shot at passing Pittsburgh (10-5) atop the AFC North in the final two weeks of the regular season.

This wasn’t Humphrey’s first momentum-shifting highlight along what has been an impressive season for the 28-year-old who welcomed the birth of his son last week.

Against Tampa Bay, he came up with two crucial interceptions that stopped the bleeding and put the ball back in the hands of the offense to put points on the board. He came up with a timely forced fumble in the second shootout with the Bengals, punching the ball loose from running back Chase Brown. Harbaugh said that night, “We talk a lot about momentum. When you don’t have it, you have to find a way to get it, and when you get it, you have to try to find a way to build on it and extend it. That’s a real thing.”

Baltimore’s passing defense was, at one point, ranked last in the NFL. They were the team’s Achilles heel. Humphrey felt they lost the standard of Ravens football. Two shootouts with Cincinnati and a loss in Cleveland were evidence enough of their once-poor complementary football. Perhaps no longer.

“When you see other guys make plays it makes you wanna go make plays,” wide receiver Tylan Wallace said. “Seeing them go make plays and then giving the ball back to us, like we gotta make something happen.”

As good as this Ravens offense is, come the postseason, they may need a few of those defensive knockout punches. Saturday night showed what’s possible.

Have a news tip? Contact Sam Cohn at scohn@baltsun.com, 410-332-6200 and x.com/samdcohn.