BALTIMORE -- Ryan Mallett did not have a job when the Baltimore Ravens decided to take a chance and offer him a contract just 12 days ago.

Mallett was determined to take advantage of the opportunity and spent countless hours at the team's practice facility. In his first start for the team, he took another huge step in resurrecting his career.

Mallett threw for a career-high 274 yards and the Ravens shocked the Pittsburgh Steelers with a 20-17 victory on Sunday. Baltimore swept the season series and has beaten the Steelers in five of the past six meetings. Despite the loss, Pittsburgh is still in the playoff hunt.

"I don't even know what to say right now," Mallett said. "It's an emotional time, but it's been fun."

Mallett completed 28 of 41 pass with a touchdown. He was also effective taking command of the huddle and did not have any costly turnovers.

"To operate the way he did, to change plays at the line, I think it says a lot about him, but it says a lot about our coaches as well," Ravens coach John Harbaugh said. "This kid was in (the practice facility) 24-7. This kid was in the staff meetings at night."

Ravens running back Javorius Allen recovered from some costly fumbles over the past two weeks and finished with 79 yards on 18 carries with a touchdown.

"It's execution," Allen said. "We've got a great group of guys up front that understand that defense. We play them twice a year, so the first time we could run on them and we just kept the same game plan."

Baltimore and Pittsburgh have one of the fiercest rivalries in the NFL and this game had plenty of drama.

Ravens cornerback Jimmy Smith had a 101-yard touchdown return negated by an offside penalty by linebacker Courtney Upshaw. Running back DeAngelo Williams took advantage with a 2-yard run to pull the Steelers to within 20-17 with 6:33 left in the game.

"I mean, this is not even to sound brash, but we believed the whole time we were going to beat them," Smith said. "It's Pittsburgh. So, records, scoring, doesn't matter how good they were playing coming in."

The Steelers got the ball on their own 20 with just over two minutes remaining. The Ravens' defense came up big and stopped the Steelers could on a 4th and 15 to seal the victory.

Steelers quarterback Ben Roethlisberger completed 23 of 33 passes for 272 yards and two interceptions. Williams had 84 of his 100 rushing yards in the first half with two touchdowns.

"Obviously, they did a good job stopping us today, but we still had a couple of times to make plays," Roethlisberger said. "The turnovers hurt us today."

A pair of pass interference penalties against Baltimore set up a 1-yard run by Williams that pulled the Steelers within 13-10 with 11:18 left in the third quarter. An interception by Smith gave the Ravens the ball at their own 42. Mallett then had a 39-yard pass to Chris Givens and a 34-yard strike to fullback Kyle Juszczyk. Allen completed the drive with a 3-yard touchdown run and the Ravens led 20-10 with 10:35 remaining in the game.

It was the first time in seven games Pittsburgh was held to less than 30 points.

"We're capable of beating anyone, but we're also capable of losing to anyone, particularly, if we lose the turnover battle, which we lost today," Steelers coach Mike Tomlin said. "We didn't secure the ball, we didn't get the ball."

The Steelers didn't get any closer to securing a playoff spot. Entering the day tied with Kansas City and the New York Jets in the wild-card race at 9-5, the Steelers were the only team that lost. The Chiefs' win over Cleveland clinched a playoff spot.

The Ravens got some early confidence when they stopped Williams on a 4th and 1 on the opening possession. Baltimore then drove 75 yards and took a 7-0 lead on a 8-yard pass from Mallett to wide receiver Chris Matthews.

The Steelers appeared to tie the game early in the second quarter when Roethlisberger hit wide receiver Antonio Brown for a 16-yard score. However, a review showed the receiver did not have possession and the Steelers had to settle for a 34-yard field goal by Chris Boswell.

Ravens kicker Justin Tucker responded with field goals from 37 and 50 yards to boost the margin to 13-3 at the half.

"It's a team loss," Brown said. "It's not on any one thing or individual. It's us as a whole. As the Steelers, we lost today."

NOTES: Baltimore CB Jimmy Smith was able to play despite leaving the previous game in the first quarter with a thigh injury. Smith had a pair of pass interference penalties and an interception … Steelers FB Roosevelt Nix (right foot) left the game early in the fourth quarter and could not return. He did not have a carry. … Ravens QB Jimmy Clausen was inactive after starting the past two weeks. He threw for 555 yards with two touchdowns with three interceptions in two losses.