ST. LOUIS -- Big Ben was the only postgame topic that really mattered to the Pittsburgh Steelers. Michael Vick's reaction when Ben Roethlisberger went down in the third quarter, and he had to grab his helmet and go, said it all.
"I was kind of stunned," the Steelers backup quarterback said after finishing a 12-6 victory over the St. Louis Rams on Sunday. "You never want to see a guy like Ben go down."
The Steelers scheduled an MRI Monday and Roethlisberger's left knee injury will be re-evaluated after that but coach Mike Tomlin had no other updates beyond saying, "Ben's got a knee."
Le'Veon Bell scored from a yard out in the first half in his first game back after a suspension, but the Steelers needed their defense to step up without a quarterback who has been hard to knock out.
"You grow infinitely when you pull those out," Tomlin said. "Obviously not the type of game we're searching for, but a win nonetheless."
The Rams were 2 for 10 on third down, 0 for 2 on fourth down and limited to 258 yards. Will Allen's interception with 1:56 left set up a field goal by Josh Scobee to put Pittsburgh ahead by six points.
"Fourth quarter picks are great," Allen said. "Lawrence Timmons did a great job of causing a hot throw and I was just in position."
Pittsburgh (2-1) averaged 32 points in its first two games but was held down well before Roethlisberger's leg got caught underneath him on a diving, sliding sack by Mark Barron.
Tomlin had no problem with the play.
"I just caught his leg on the way in," Barron said. "I didn't have nothing to do with his knee, I didn't see how he fell."
The Rams (1-2) were limited to two field goals by Greg Zuerlein and have scored just 16 points the last two games. Their last chance ended when the Steelers successfully challenged a potential first-down catch by Kenny Britt near midfield with 1:19 to play.
"I thought I had the ball coming down, I threw it back to the ref after I Ianded," Britt said. "I made the catch and they decided if it's a catch or not."
Roethlisberger hasn't missed a game since late in 2012. He won his franchise-record 108th game, passing Hall of Famer Terry Bradshaw, while going 20 of 24 for 192 yards and an interception.
"We'll be saying those prayers for Big Ben," Rams quarterback Nick Foles said.
Vick was 5 of 6 for 38 yards and had two carries for minus-2 yards.
Attendance of 52,433 included thousands of Pittsburgh faithful waving Terrible Towels and disrupting the Rams offense at times. The Steelers fan boost still left the Edward Jones Dome more than 13,000 shy of capacity.
Antonio Brown had 11 catches for 108 yards, his third straight 100-yard receiving game.
Both teams had running backs make debuts and Bell's production was far superior to that of Rams rookie Todd Gurley.
Bell had 62 yards on 19 carries. Gurley, who did not start and split time with Tre Mason, had just 9 yards on six carries.
Scobee's short field goal and a 1-yard run by Bell put Pittsburgh up 9-0 early, although it failed on the 2-point conversion for the first time in four chances when Roethlisberger threw incomplete.
The Steelers were fooled on a fake punt at midfield in the second quarter but Stedman Bailey couldn't scoop Johnny Hekker's underthrown ball before it hit the turf.
Kickoff was delayed about 26 minutes by a small fire near a corner of the south end zone from sparks emitted by a pyrotechnic display during Rams player introductions. The cleanup job was hampered by a malfunctioning wet-dry vacuum that spewed collective material back out.
Neither team made any plays near a circular mark between the 3 and 4-yard line.
Notes: Rams MLB James Laurinaitis became the franchise career tackle leader, passing late Hall of Famer Merlin Olsen. Laurinaitis has started all 99 games since being drafted in the second round in 2009. ... The Steelers said backup TE Matt Spaeth (hand) will be evaluated. ...Rams backup CB Maurice Alexander (groin) was injured in the second half.