Sheldon Rankins of the Jets celebrates his sack during the fourth quarter...

Sheldon Rankins of the Jets celebrates his sack during the fourth quarter against the Bengals at MetLife Stadium on Sunday. Credit: Jim McIsaac

PITTSBURGH — C.J. Mosley was watching film of the Steelers’ first three games and found them almost unrecognizable.

Mosley faced Pittsburgh 10 times with Baltimore, so he has known the team well. Not anymore. Ben Roethlisberger retired last year after 18 seasons with the Steelers and Mitch Trubisky is running the offense now. They’re no longer a pass-heavy team, and that took some getting used to for Mosley.

“When I was watching film, it kind of caught me by surprise,” he said. “Not used to seeing all the big linemen, all the power, all the counters, all the different run schemes. They’re going to take their shots when they can.

“When you think about the old-school Steelers and you think Big Ben and those guys, it’s definitely not that type of team anymore.”

This should be a welcome change for a struggling Jets defense on Sunday.

The Steelers (1-2) rank next-to-last in the NFL in yards per game (272.7), are 28th in passing yards (182.7) and are tied with the Jets with five touchdowns.

Running back Najee Harris ran for 1,200 yards as a rookie and Diontae Johnson had more than 1,161 receiving yards last season, but they’ve started slowly.

This matchup could be the remedy the Jets’ failing and ailing defense needs.

The Jets (1-2) opened against three explosive teams and struggled to stop the Ravens, Browns and Bengals. The common issues have been giving up big plays, not getting off the field on third down and miscommunications and breakdowns in the secondary.

Those teams converted 51.3% of their third downs, including seven touchdowns.

Defensive coordinator Jeff Ulbrich said they identified some of the problems during practice this past week, corrected them and simplified some things. Ulbrich believes the Jets will be a different team on Sunday against a team that has “a lot of offensive variety in their playbook.”

“It’s improving what we’re doing for sure and then it’s also maybe doing a little bit less until we get to the place where we master what we have,” Ulbrich said. “We’ll keep going forward with that approach.”

Robert Saleh and Ulbrich have drawn plenty of criticism for the Jets’ defensive performance. It’s been somewhat surprising because Saleh made his bones on that side of the ball.

The Jets were ranked last or near the bottom in most categories last season. They improved the overall talent on defense, so more was expected in Year 2 in this system. This group has shown some improvements in the running game, but allowing explosive plays and third-down conversions continues to hurt them.

“Some self-inflicted things that we’ve been on the unlucky end of have resulted in huge plays and touchdowns,” tackle Sheldon Rankins said. “It’s something we have to have that urgency about to fix going forward.”

Rankins was vocal during training camp about his belief that the Jets could be the NFL’s No. 1 defense and have a number of guys “who can wreck games.” That certainly hasn’t been the case thus far. The Jets have five sacks and three takeaways.

Big-ticket edge rusher Carl Lawson has half a sack. Safeties Jordan Whitehead and LaMarcus Joyner have allowed big plays and compounded that last week against Cincinnati with a huge missed tackle (Whitehead) and a 15-yard personal-foul penalty (Joyner). Rookie Sauce Gardner has played well, but he’s been a part of some communication breakdowns that led to TDs.

Rankins said there has to be more urgency and accountability.

“We can’t just say, ‘Oh, we’ll get it’ or ‘Oh, I got you,’ ” Rankins said. “We can’t take that approach because it’s just a loser’s mentality. I’ve been lucky to be around some good teams and understand that the way you do anything is the way you do everything. For us, everybody’s got to have that accountability within themselves and with the man next to you.

“We have to get this thing figured out now because if you finally get it done in Week 9, the season could easily have slipped away from you. Now you’re playing catch-up. We have the guys to do it, the talent, and we also have the leaders to get it done. It’s just a matter of getting that [expletive] done.”

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