The New York Giants rallied from 21 points down to win 31-28 at the Arizona Cardinals in a remarkable franchise-record-equalling comeback on Sunday.
The Giants lost their opening game 40-0 to Dallas last week and had statisticians scrambling for details on the worst ever starts to an NFL season when they trailed 20-0 at half-time.
But quarterback Daniel Jones set about orchestrating a stunning turnaround with a 13-yard rushing touchdown early in the third.
New York put up 24 unanswered points in the remainder of the game before Graham Gano slotted a 34-yard field goal with 19 seconds left on the clock to put the Giants ahead.
Jones ended the game with three total touchdowns having thrown for 321 yards and rushed for another 59.
Running back Saquon Barkley had two touchdowns and rushed for 63 yards but had to come out of the game in the final stages with what appeared to be a serious ankle injury.
The 21-point comeback is the biggest by the Giants in the modern NFL era and matches wins against the Chicago Cardinals in 1949 and the Philadelphia Eagles four years earlier.
Washington trailed 21-3 in the second, before they put up 18 unanswered points and then two rushing touchdowns from Brian Robinson Jr in the fourth quarter put them 11 points up.
A field goal for Denver narrowed the gap and then with the clock running out a "Hail Mary" pass from Broncos quarterback Russell Wilson was tipped on and eventually collected in the end zone by Brandon Johnson to give Denver the chance of a comeback of their own.
They were unable to make the two-point conversion needed to force overtime, leaving their new coach Sean Payton with a 0-2 start to the season.
Reigning NFL Most Valuable Player Mahomes overcame a slow start to finish with 305 yards from 29-of-41 passes to give the reigning Super Bowl champions a gritty 17-9 win on the road in Florida.
Mahomes and the Chiefs had been upset at home by the Detroit Lions in their opening game of the season after a litany of blunders by the receiving corps.
- Kelce returns -
But with fit-again tight end Travis Kelce back in the starting line-up, Mahomes looked more like his old self as the Chiefs dug deep for a hard-earned victory.
Mahomes picked out favourite target Kelce for a third-quarter touchdown after earlier connecting with Skyy Moore for the Chiefs' other touchdown.
The Jets, who lost quarterback Aaron Rodgers for the season after he snapped his achilles tendon in the win over Buffalo on Monday, had little joy against an impressive Cowboys defense.
But while the Chiefs and Bills got back to winning ways, the Cincinnati Bengals fell to 0-2 after a 27-24 loss to divisional rivals Baltimore.
Raheem Mostert scored with two rushing two touchdowns including the 43-yard fourth quarter touchdown that ultimately proved decisive.
The Patriots made it a seven-point game with Rhamondre Stevenson's two-yard run but lost the game when their play on fourth down, where they had creatively kept the ball alive rugby style, was ruled to have been short on review.
In Detroit, Lions quarterback Jared Goff's bid to set a new NFL record for the longest passing streak without an interception came to an abrupt end in a 37-31 overtime defeat to the Seattle Seahawks in Motor City.