PITTSBURGH —The green grass of Heinz Field is one of the flatter parts of Pittsburgh's landscape of curvy, hilly roads and steep bluffs that rise quickly from the river banks, but the Vikings felt like they were going uphill for most of Sunday's game.

The Steelers capitalized on penalties and significant gains on long pass plays to build a 14-point lead and turned up the pressure on the Vikings offensive line and quarterback Case Keenum, who was making his first start with the Vikings and against the Steelers, who claimed a 26-9 win in their home opener.

After Keenum connected with Adam Thielen for a gain of 24 to the Pittsburgh 24-yard line early in the second quarter, the Steelers brought extra heat on consecutive plays and successfully forced an errant pass intended for an open Stefon Diggs.

"We'd seen a lot of that on film, but they dialed up three in a row," Keenum said. "We actually had Diggs, on I think it was the second play, in the end zone. I tried to get it to him, but Pittsburgh did a good job of dialing them up today."

Minnesota was forced to settle for a 42-yard field goal on the drive for its only points of the first half.

Of the Vikings 12 possessions, six included at least one penalty or negative play to put them in adverse down-and-distance situations.

Another clean possession resulted in a touchdown for the Vikings, making it a 17-9 game with nearly 10 minutes left in the third quarter.

Pittsburgh responded with a field goal, and Minnesota tried to answer but had a 23-yard completion from Keenum to Diggs wiped off on an offensive pass interference call. The Vikings converted third-and-20 with a great catch by Kyle Rudolph for a gain of 27, but they suffered a holding call on Nick Easton two plays later.

"When you're fighting uphill against second-and-20, that puts us behind schedule and doesn't allow us to do the things that we do well on offense, so that was the biggest thing for us today, just shooting ourselves in the foot, and that's some of the things we did last year to cost us games," Rudolph said.

"We have to get positive yardage on first downs and give [Offensive Coordinator] Pat [Shurmur] a manageable second down so he can make whatever call he wants," Rudolph added. "Last week, all we talked about was how balanced we were. That's cause we were able to stay ahead of the chains."

The Vikings were assessed 131 yards on 11 penalties. Officials flagged Pittsburgh 10 times, but the damage on those infractions was only 72 yards.

On backing up Bradford

Keenum found out on Sunday morning that he would be starting in place of Kyle Rudolph, who was dealing with a knee injury that limited him in practice all week. Bradford was crisp in Week 1, completing 27 of 32 passes for 346 yards and three touchdowns en route to earning NFC Offensive Player of the Week honors.

Players and Head Coach Mike Zimmer said they thought Keenum fought hard.

"I thought Case gave us a chance to go out there and win today," Rudolph said. "He fought his tail off, stood in there and made some big throws and gave us a chance to win the game."

Keenum completed 20 of 37 passes for 167 yards for a passer rating of 65.9. He was sacked two times, and press box statisticians counted seven quarterback hits by Pittsburgh defenders against a Minnesota offensive line that was playing just its second game as a unit.

"I think it was hard," Zimmer said. "He was under duress, it was really hard to tell. I can't see who is open and not open. I know he battled."

Zimmer was asked about Bradford and said, "He couldn't play."

"[The injury rehab is] not surgical," Zimmer said. "He's had two surgeries on the knee, sometimes it swells up. I'm not going to talk about injuries, I'm not going to talk about Bradford's knee. I'm just not going to talk about it."

Penalty to points

The Vikings were unsuccessful on a fake punt during their first possession of the second half and turned over the ball on downs at their own 36-yard line.

Minnesota's defense responded by allowing just three net yards and forcing a 51-yard field goal attempt by Chris Boswell. The kick was wide left, but Minnesota's Tom Johnson was called for an illegal formation. Pittsburgh was awarded five yards, and Boswell's kick from 46 was on the mark for a 17-3 lead.

"Supposedly we were covering part of the center [long snapper]," Zimmer said.

Johnson was surprised by the call.

"The ref said something about my arm was still in the area, but he had already stood up," Johnson said. "He basically stands over the center and tells you you're good. From what we were seeing on film, I was still good.

"Coach Prief' (Special Teams Coordinator Mike Priefer) tells us the ref will stand over the center, get your distance and make sure you don't have any part of you on the snapper," Johnson added. "It's a new rule. I don't know. From what we saw, [Eric] Kendricks was telling me to bump over, tighten up, so we thought we were legit. It's a call that we don't know too much about."

"Bus-like" stat line

Fullback C.J. Ham's career stat line: one carry, one yard, one touchdown.

Ham's power run into the end zone on Sunday was somewhat fitting that it occurred in Pittsburgh, where "The Bus" Jerome Bettis spent 10 of his Hall of Fame seasons. Bettis once rushed five times for 1 net yard and three touchdowns in a game.

Ham got the opportunity after a 25-yard run by Dalvin Cook, who was initially awarded an extra yard and a touchdown. The call, however, was reversed, so Cook is still awaiting his first score.

"I definitely didn't want to take that from him. That was a great run, but they called my number and we got it done," Ham said. "It was a moment I'll never forget. It was awesome to score, but it's all about the team. It would have felt a lot better getting the win and scoring my first touchdown."

Another record for Sherels

Marcus Sherels became the franchise leader in punt return yardage. He entered the game three yards shy of Leo Lewis (1,812) and took back his only punt return 12 yards, giving him 1,821 career punt return yards.

Sherels also has franchise career records with five punt return touchdowns, seven punt returns of more than 50 yards and the single-season record for average (15.2).