The NFL said in a statement Monday that the penalty should have been called by referee Bill Leavy's crew, moving the ball 5 yards closer to the end zone and giving Succop another attempt at the game-winning field goal. Succop was 15 of 16 this season from within 40 yards.
The NFL did not say whether Leavy's crew would be disciplined.
Chiefs coach Andy Reid actually called his final timeout after the missed field goal and tried to convince the officiating crew of the illegal formation. But because illegal formations are not reviewable, Reid had no other recourse and the play stood.
"I called a timeout right there. That was for a reason," Reid said. "I couldn't challenge, all I had was a timeout, so maybe they'd take a peek and read through the timeout and see what took place, but listen, human error. ... There's not much more you can say."
The outcome of the game didn't have any bearing on the Chiefs, who rested most of their starters. Kansas City was already assured of the No. 5 seed in the AFC playoffs and will head to Indianapolis on Saturday for a rematch of a game won two weeks ago by the Colts.
The result had significant repercussions for the Chargers and Steelers, though.
San Diego (9-7) earned the final AFC playoff spot when Nick Novak kicked a 36-yard field goal in overtime to win the game. The Chargers will visit Cincinnati in the wild-card round Sunday.
The Steelers (8-8), meanwhile, would have claimed the playoff spot through a series of tiebreakers had Kansas City won, and Pittsburgh coach Mike Tomlin even said Monday he knew the Chargers were lined up illegally before the field goal attempt.
"What transpired yesterday was unfortunate for our hopes moving forward. We'll have to find a way to accept that and move forward," Tomlin said. "I'm not going to lose any sleep over something that happened in a stadium that we weren't even in."
AP Sports Writers Dave Skretta in Kansas City, Mo., and Will Graves in Pittsburgh contributed to this report.
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