KANSAS CITY, Mo. (AP) Alex Smith squirmed out of the pile in the end zone, got to his feet and let out a roar.
All it took was the largest comeback in the 56-year history of the Kansas City Chiefs for the stoic quarterback with the California cool to finally let some emotion show.
Smith threw for 363 yards and two touchdowns to rally his team from a three-touchdown hole, then scored on third-and-goal on the first possession of overtime for a heart-stopping 33-27 victory over the San Diego Chargers in their season opener Sunday.
''Lot of emotion at the end of the game,'' Smith said with a smile.
The Chiefs trailed 24-3 in the second half before mounting their charge, and it really kicked into gear when Smith hit Jeremy Maclin with a back-shoulder fade to get within 27-17 with 9 minutes to go.
Cairo Santos added a 33-yard field goal a few minutes later. Then, after forcing a three-and-out, Spencer Ware finished a four-play drive with a touchdown plunge to knot the game at 27.
It took Kansas City 10 plays to march 75 yards in overtime. Smith finished it with his plunge from the 2-yard line, keeping the ball rather than pitch when the smallest of creases opened.
By the time Smith reached his feet, the Chiefs had flooded onto the field to celebrate.
''You're going to have games like this that show your character, show your grit,'' coach Andy Reid said. ''I'm proud of the way they handled it. They had confidence in each other.''
Philip Rivers threw for 243 yards and a touchdown, and Melvin Gordon scored the first two TDs of his career. But the Chargers were unable to keep any drives going in the fourth quarter, when the Chiefs were charging to their NFL-leading 11th consecutive regular-season victory.
''You just can't let them back in. We've got to close it,'' Chargers offensive tackle Joe Barksdale said. ''Everybody with eyes who saw the game has got to know, we have to close it. It's not acceptable to be up by 24-3 and lose the game. We know that.''
The collapse came after San Diego wide receiver Keenan Allen left in the second quarter with what appeared to be a serious knee injury. He already had six catches for 63 yards.
Even without Allen, the retooled Chargers and their improved offensive line managed to build a 21-3 halftime lead. And it looked as if their eight-game skid against AFC West rivals would finally end.
That all changed once the fourth quarter began.
Josh Lambo missed a 54-yard field goal with San Diego leading 27-10, and the momentum swung toward Kansas City. Smith calmly completed six passes and marched his team 56 yards to the end zone, Santos hit his field goal and Ware his touchdown run, and the game was headed to overtime.
The Chiefs carried their newfound momentum all the way to the finish.
Chiefs cornerback Marcus Peters held a black-gloved fist aloft during the national anthem in a salute reminiscent of Tommie Smith and John Carlos at the 1968 Mexico City Olympics. It was his way of standing beside 49ers quarterback Colin Kaepernick's stance on social injustice.
''I'm supporting Colin and what he's doing, as far as raising awareness with the justice system,'' said Peters, who grew up in Oakland, California. ''Coach said it was OK if I wanted to express my thoughts about what I wanted to do, so I just expressed it.''
Peters did link his left arm with his teammates as country singer Trace Adkins performed the anthem. The Chiefs said in a statement they decided to lock arms in a show of solidarity.
The Chiefs played without star pass rusher Justin Houston , who could be out until November as he recovers from ACL surgery in February. The Chargers were without defensive end Joey Bosa, the third pick in April's draft, who remained on the exempt list after a lengthy holdout.
RUNNING IT: Ware finished with 70 yards rushing and had seven catches for 129 yards, giving the Chiefs a big boost without Jamaal Charles. The four-time Pro Bowl running back is still recovering from surgery last season to repair his ACL and was inactive Sunday.
Allen missed the final eight games last season with a lacerated kidney , and now could be out the rest of this season. He never put weight on his right knee after going down Sunday.
''There is speculation about an ACL,'' coach Mike McCoy said, ''but we'll run tests when we get back home.''
Chiefs linebacker Sam Barrington left in the second half with a hamstring injury.
AP NFL website: www.pro32.ap.org and AP NFL Twitter feed: www.twitter.com/AP-NFL