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PITTSBURGH -- Their franchise quarterback on his way to the hospital, the momentum firmly on the other side of the field after a stunning last-minute rally by one the NFL's worst teams, the Pittsburgh Steelers appeared lost.

Then linebacker Lawrence Timmons provided a reminder that -- Ben Roethlisberger or no Ben Roethlisberger -- Pittsburgh's identity begins and ends with defense.

Timmons intercepted Kansas City quarterback Matt Cassel on the second snap of overtime and Shaun Suisham drilled a 23-yard field goal one play later to lift the Steelers to a 16-13 victory over the hapless Chiefs.

"We just stayed positive," Timmons said. "It's easy to get down on yourself, but we are not like that. We stand up, face adversity."

Good thing, because there's plenty to go around.

The Steelers (6-3) have won four straight but played most of the second half without Roethlisberger, who left with a right shoulder injury in the third quarter after getting sacked by Kansas City linebackers Tamba Hali and Justin Houston.

Coach Mike Tomlin wouldn't speculate on the severity of Roethlisberger's injury and his status for Sunday's showdown with AFC North leader Baltimore is uncertain.

"It didn't seem like a tough hit ... but he came to the sideline and next thing you know he was gone," Pittsburgh left tackle Max Starks said. "I'm hoping it was nothing serious. Honestly it didn't seem like it."

Veteran backup Byron Leftwich came on in relief and completed 7 of 14 passes for 73 yards in his first regular season game in nearly two years.

"It wasn't a pretty body of work by any of us, but his consistency remains the same in terms of being a stabilizing force for us," Tomlin said.

Jamaal Charles ran for 100 yards and a score for the Chiefs (1-8), who have lost six straight.

The Chiefs had their chances, taking their first lead in regulation all season in the first half then overcoming a series of embarrassing miscues to tie the game at 13 at the end of regulation.

Taking over at the Kansas City 20 with 1:51 remaining, Cassel led the Chiefs 52 yards -- converting a 4th-and-15 in the process -- to set up a 46-yard field goal by Ryan Succop as time expired.

"I thought our guys played and competed all night long," Cassel said. "We went up against a good football team and unfortunately we weren't able to pull it out in the end but I thought the way the guys handled the environment of Monday Night Football was great."

Kansas City's only other victory this season came in overtime, a stunning upset in New Orleans in September. Any chance at a repeat faded when Cassel's pass on the second play of the extra period landed in the hands of Timmons, who returned it 23 yards to set up Suisham's second game-winning field goal of the season.

It was sweet vindication for a Pittsburgh defense that allowed AFC lesser lights Tennessee and Oakland to mount fourth-quarter comebacks earlier this season. Though the Steelers only managed to get the Chiefs -- last in the NFL in turnover differential -- to cough it up once, timing is everything.

"We got the one that count baby," linebacker Larry Foote said. "We got the one that count. They did a good job tonight, but we got the one that was big time."

Tomlin didn't waste any time, sending the field goal team out immediately. Suisham's kick was good all the way, and now the Steelers begin a critical three-game stretch wondering when their two-time Super Bowl winning quarterback will be ready.

Roethlisberger is in the midst of a career year but struggled through a so-so first half and was 9 of 18 for 84 yards and a touchdown when he tried to buy time in the pocket hoping to convert on third-and-4. Hali and Houston swarmed in and sent him into the turf, driving his throwing shoulder into the ground.

Enter Leftwich, who managed to lead the Steelers on one scoring drive early in the fourth that gave them a 13-10 lead.

"After four or five plays, it was like riding a bike," Leftwich said. "I took a few hits. I hadn't hit the ground in awhile. It was a whole lot of things I hadn't done in awhile. It was good."

Pittsburgh came in riding a three-game winning streak that erased the sour taste of a 2-3 start, and the Steelers insisted all week they wouldn't look past the Chiefs.

Funny, Pittsburgh certainly looked distracted at the start of a raw, soggy night at Heinz Field.

The Chiefs didn't take long to erase one bit of misery in their lifeless, luckless season, taking their first lead since New Year's Day during a spirited first half in which they avoided the kind of gaffes -- turnovers, penalties, assignment breakdowns -- that have plagued them all year.

With Charles gashing Pittsburgh's defensive line and Cassel avoiding mistakes, Kansas City raced in front 10-0. Cassel hit Tony Moeaki for 38 yards on the Chiefs' second drive, setting up a 12-yard touchdown run by Charles to give Kansas City its first lead since a 7-3 victory over Denver in the 2011 regular-season finale.

The lead grew to 10-0 after an Isaac Redman fumble deep in Pittsburgh territory led to a 22-yard field goal by Succop.

"I think we played well in all phases," Cassel said. "That was the first time we played well together this year."

Like any brief flirtation with success for Kansas City, it didn't last. The Steelers pulled even at halftime on a 35-yard field goal by Suisham and a remarkable 7-yard touchdown grab in the corner of the end zone. The ball slid through Wallace's hands, but he secured it with his legs -- and controlled it -- before rolling out of bounds.

There would be no second-half carryover, however. Whatever energy the Steelers had vanished the second Roethlisberger trudged to the sideline holding his right shoulder.

In that moment all the chatter about Kansas City's visit and former Chiefs coach turned Pittsburgh offensive coordinator Todd Haley's shot at revenge vanished.

Game notes

The Steelers have won 15 consecutive home games on Monday night ... Roethlisberger topped 1,000 career rushing yards with a 13-yard scramble in the first half ... Pittsburgh S Ryan Clark left the game in the fourth quarter with a concussion.