PITTSBURGH — Coming off one of their most disappointing losses in the 14-year history of Heinz Field, the Steelers head to winless Jacksonville not quite knowing what to expect.

Tampa Bay picked up its first victory of the season by coming back from seven points down behind backup quarterback Mike Glennon, who passed for 245 of his 302 yards in the second half.

Pittsburgh’s offense will have to step it up more than it did on Sunday because there are going to be plenty more games like that against the Steelers defense. Their cornerbacks are weak and they are getting little pass rush — one sack on Sunday. No pressure and poor cornerback play is a deadly combination.

“That’s something that we have to do better at if we want to win,” defensive end Brett Keisel said. “We have to get consistent pressure on the quarterback. … Rush and coverage work together and we have got to pin our ears back and get to him if we expect to win.”

Pittsburgh plays at Jacksonville next Sunday and the Jaguars are 0-4. Then the Steelers play at Cleveland.

Tampa Bay was supposed to be the start of a soft schedule that would allow the Steelers to perhaps reverse their 2-6 start of last season by going 6-2. Those next two games, though, look as though they are must wins at this point if they want to entertain making the playoffs for the first time since 2011.

“We’ve got work to do, obviously,” Keisel said. “And I hate saying that, but we do. We got to cut out the mistakes, that’s what’s beating us, mistakes against ourselves. We can’t go out and expect to play and beat an NFL team and beat ourselves as well.

“It’s too hard.”

NOTES, QUOTES

–Wide receiver WR Antonio Brown set a NFL record by catching at least five passes for 50 yards in 20 consecutive games. Lavernanues Coles and Brown had been tied.

–K Shaun Suisham extended his club-record of 24 consecutive field goals made without a miss until he missed one from 50 yards in the first half.

–The Steelers have committed 44 penalties for 387 yards, second most in each category in the NFL.

“The bottom line is that we are an undisciplined group,” coach Mike Tomlin said. “We are too highly penalized. Obviously we are not coaching it. We are allowing it to happen. So I take responsibility for that. We are not going to win close football games being penalized in the manner in which we’ve been penalized over the first month of the season. It’s unacceptable. It’s inexcusable.”

REPORT CARD VS. BUCCANEERS

PASSING OFFENSE: C — Ben Roethlisberger was sacked five times and lost a fumble on one of them at his 9-yard line that led to Tampa Bay’s first touchdown. He missed a couple of wide open receivers and had at least four of them drop passes, one that would have been a 78-yard touchdown by Antonio Brown. Nevertheless, he did complete 29 of 40 for 314 yards, three touchdowns and no interceptions for a 120.2 passer rating.

RUSHING OFFENSE: D — After having two backs top 100 yards for the first time in 28 years a week earlier, the Steelers could not total 100 on Sunday. They had 85 yards and averaged 3.1 per carry. Le’Veon Bell led them with 63 and a 3.3-yard average. LeGarrette Blount carried just four times and had 25 yards.

PASS DEFENSE: F — Backup quarterback Mike Glennon completed 21 of 42 passes for 302 yards and two touchdowns, including the winner with 7 seconds left from five yards away after he completed a 41-yarder to set that up. He was intercepted once only because rookie Mike Evans had to stop when he pulled a groin on a deep route. Glennon was sacked just once.

RUSH DEFENSE: B — Tampa Bay managed 63 yards on 20 carries, with one touchdown run of three yards by Doug Martin in the third quarter.

SPECIAL TEAMS: F — With the ball at their 17 and 50 seconds left, Brad Wing got off just a 29-yard punt and Tampa Bay took over with 40 seconds and no time outs and drove for the winning touchdown. The Steelers also gave up one 25-yard punt return and Shaun Suisham missed a 50-yard field goal at the end of the first half after Bucs rookie Patrick Murray hit one from the same spot earlier.

COACHING: F — With a 24-17 lead late in the third quarter and a fourth-and-three at Tampa Bay’s 37, Mike Tomlin had Ben Roethlisberger pooch-punt. There was a five-yard false start penalty on the play and the Steelers wound up punting from the 42. But they had a chance to virtually put the game away there and played conservatively. Also, the Steelers committed 13 penalties for 125 yards and even Tomlin called his team an “undisciplined group.” That reflects badly on him and his staff.