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 home victory over the San Diego Chargers on 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 for a 19-yard score, pulling to within 27-17 with nine 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 5-yard TD plunge to knot the game at 27.

It took Kansas City 10 plays to march 75 yards in overtime. Smith finished it with his rush from the 2, keeping the ball rather than pitch it 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 score for San Diego.

Melvin Gordon scored the first two touchdowns 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.

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.

Bengals 23, Jets 22 — Mike Nugent kicked a 47-yard field goal with 54 seconds left, lifting Cincinnati to a back-and-forth, season-opening victory in East Rutherford, N.J. Andy Dalton threw for 366 yards and a touchdown, but was sacked a career-high seven times.

A.J. Green caught 12 passes for 180 yards, mostly against Darrelle Revis, to help the Bengals beat the Jets for the first time in 10 meetings in New Jersey.

Josh Shaw sealed the victory with an interception of Ryan Fitzpatrick in the closing seconds, helping Cincinnati improve to 7-7 in openers under coach Marvin Lewis.

Nick Folk kicked a go-ahead 23-yard field goal with 3:23 remaining, but Dalton marched the Bengals downfield for the winning drive. The first missed extra point in Folk’s career and a blocked 22-yard field goal attempt came back to haunt the Jets.

Raiders 35, Saints 34 — Oakland gambled with a 2-point conversion that Derek Carr converted with a pass to Michael Crabtree for the winning points with 47 seconds left, after host New Orleans gave up a touchdown on Carr’s 10-yard pass to Seth Roberts.

‘‘Everyone knew about our strategy,’’ said Raiders coach Jack Del Rio. “I didn’t really ask for any feedback there. I said, ‘When we score here, we are going to go for 2 and win it right here.’ ’’

Oakland had to overcome a 14-point, second-half deficit and a 424-yard, four-TD performance by Drew Brees. It also had to sweat out rookie kicker Wil Lutz’s last-second field goal attempt from 61 yards, which narrowly missed wide left.

Brees’s touchdowns included a franchise-record 98-yarder to Brandin Cooks.

Carr finished with 319 yards and one touchdown passing, and Jalen Richard ran 75 yards on his first NFL carry for a score.

Lions 39, Colts 35 — Matt Prater redeemed himself for an earlier missed PAT by kicking a 43-yard field goal with eight seconds left, and Detroit rallied in Indianapolis just 37 seconds after it looked like Andrew Luck had led the Colts to victory.

After Prater’s miss, Luck drove the Colts 75 yards and hooked up with Jack Doyle on a 6-yard TD pass with 37 seconds left. Adam Vinatieri’s extra point gave the Colts a 35-34 lead.

Matthew Stafford, who was 31 of 39 for 340 yards with three touchdowns and no interceptions, quickly got the Lions into position for Prater to atone. Indy was called for a safety on the ensuing onside kick, the final play of the game.

Luck was 31 of 47 for 385 yards with four touchdowns and had no turnovers.

Seahawks 12, Dolphins 10 — Hobbled by an ankle injury, Russell Wilson pulled off another fourth-quarter comeback, throwing a 2-yard TD pass to Doug Baldwin with 31 seconds left as Seattle sneaked past visiting Miami.

An 86-yard touchdown drive by Ryan Tannehill gave the Dolphins a 10-6 lead with 4:08 remaining. But Seattle went to work, converting twice on fourth down on the winning march.

Giants 20, Cowboys 19 — Eli Manning threw for three touchdowns, including the go-ahead score to Victor Cruz in his first game in nearly two years, and the Giants prevailed in Arlington, Texas, to win the head coaching debut of Ben McAdoo.

The game ended with Dallas in position for a roughly 57-yard field goal, but Terrance Williams didn’t get out of bounds after a catch and the clock ran out. Dan Bailey had four field goals for the Cowboys, including from 56 and 54 yards.

Eagles 29, Browns 10 — Carson Wentz had a stellar NFL debut for host Philadelphia, passing for 278 yards and two scores in Cleveland.

Promoted from No. 3 quarterback to starter just eight days ago, the No. 2 overall pick from North Dakota State finished 22 of 37 with a 101.0 passer rating.

Wentz threw a 19-yard TD pass to Jordan Matthews on the opening drive and tossed a perfect 35-yard TD pass down the right side to Nelson Agholor for a 22-10 lead in the third.

Ravens 13, Bills 7 — Baltimore used a TD pass by Joe Flacco, two field goals, and a throwback defensive performance to win its season opener at home. The Ravens limited Buffalo to 160 total yards and sacked Tyrod Taylor twice.

Returning from a knee injury that ended his season last November, Flacco went 23 of 34 for 258 yards, including a 66-yard touchdown pass to newcomer Mike Wallace in the second quarter that put the Ravens ahead for good. Justin Tucker had field goals of 50 and 37 yards.

Packers 27, Jaguars 23 — Aaron Rodgers threw two TD passes — including one to Jordy Nelson, who played in his first game since Jan. 18, 2015 — and ran for another score in leading Green Bay in sweltering Jacksonville, Fla.

The Jaguars’ Blake Bortles completed 24 of 39 passes for 320 yards, with a touchdown and an interception.

Texans 23, Bears 14 — New franchise quarterback Brock Osweiler looked worth the big contract, passing for 231 yards and two touchdowns in guiding Houston at home.

First-round pick Will Fuller became the first player in franchise history to have 100 yards receiving in a debut, finishing with 107 and a touchdown. DeAndre Hopkins added 54 yards and a score and running back Lamar Miller had 106 yards rushing in his first game with the Texans.

Chicago’s Jay Cutler threw for 216 yards with a touchdown and an interception, and was also sacked five times.

Vikings 25, Titans 16 — With Adrian Peterson getting bottled up in Nashville, Minnesota needed its defense to step up. Eric Kendricks returned an interception 77 yards for a touchdown and Danielle Hunter scored on a 24-yard fumble return.

The Vikings scored 25 straight points after being shut out in the first half. They also forced three turnovers in the span of just under seven minutes.

Tennessee focused on stopping Peterson, who had just 31 yards on 19 carries. Named starting quarterback late last week, Shaun Hill was 18 of 33 for 236 yards.

Buccaneers 31, Falcons 24 — At Atlanta, Jameis Winston threw four touchdown passes for the second time in his young career and finished 23 of 33 for 281 yards for Tampa Bay.

Former Falcons offensive coordinator Dirk Koetter was a winner in his debut as an NFL head coach.