PITTSBURGH >> The Tennessee Titans feel like they missed an opportunity.

Quarterback Marcus Mariota threw four interceptions and the defense experienced a second-half meltdown as Ben Roethlisberger and the Pittsburgh Steelers routed the Titans 40-17 tonight.

“We can’t make some of those mistakes, we can’t miss opportunities that we had,” Titans coach Mike Mularkey said. “Against good teams, it’s going to cost you. You’re going to get beat bad.”

Mariota battled ankle and shoulder injuries but played through the pain to finish 22 of 33 for 306 yards with a touchdown and four interceptions. Roethlisberger ended 30 of 45 for 299 yards with four touchdowns for Pittsburgh. Antonio Brown caught 10 passes for 144 yards and three scores.

“It’s just frustrating because at the end of the day, I still feel like we played good defense,” Titans safety Kevin Byard said. “We just didn’t play good enough to win, and that’s the frustrating part.”

Too many mistakes cost the Titans.

Mariota threw two interceptions in the first half, and a blocked field goal in the second quarter ended another possession as the Titans trailed just 16-7 at halftime.

Rishard Matthews, who finished with five receptions for 113 yards, caught a 75-yard touchdown to open the second half. That put the Titans behind 16-14, but Roethlisberger and the Steelers responded. The Titans had a chance to answer Brown’s second score, but Delanie Walker dropped a sure touchdown pass in the end zone. That led to a Titans’ field goal, a 23-17 deficit, and the last points Tennessee scored all night.

“I thought we started the half great, but you can’t expect them to lay over,” Mariota said. “They’re going to find ways to make plays and build on their lead. When we have our opportunities, we have to find a way to make plays.”

The Titans entered winners of four straight and tied with Jacksonville atop the AFC South. Tennessee sought its first 7-3 start since 2008. More importantly, the streaking Titans — who are looking to snap an eight-season playoff drought — wanted to show they belonged as a contender in the conference.

“We can’t win games if we make that many mistakes against a great team like the Pittsburgh Steelers, especially at a big atmosphere like Heinz Field,” Byard said. “I feel like we made some plays, don’t get me wrong. But we just didn’t make enough.”

The Titans’ defense held firm through one half until Pittsburgh broke it open in the second half and scored points on its first four possessions.

Two Mariota interceptions in the first half were returned deep into Titans’ territory. But the Steelers, 31st in red zone touchdown percentage entering the game, only came away with six points and a nine-point halftime lead.

Roethlisberger was an efficient 4 of 5 for 71 yards and a touchdown on the Steelers’ first drive, but he was held in check the rest of the half, completing just 6 of 17 passes for 43 yards.

That changed in the second half.

Roethlisberger opened the second half 17 of 20 for 165 yards and three touchdowns, as he orchestrated four second-half scoring drives and turned a two-point lead early in the third quarter into a blowout.

The Titans enjoyed a promising start to the second half, when Mariota connected with Matthews for the long touchdown.

It all went downhill from there thanks to a breakout effort from Roethlisberger and the Steelers’ offense. Walker’s end-zone drop and two more Mariota interceptions in the second half didn’t help the comeback effort.

“It’s a disappointing loss,” Mularkey said. “We made too many critical mistakes against a really good football team and it caught up to us in the second half. We had opportunities to make it more of a game and we failed to do so.”