ENGLEWOOD, Colo. – Peyton Manning is only getting better with age.

Those surgical scars on his neck are starting to fade like all those fears he might never be the same quarterback — or even play again — after his right arm shrank from a damaged nerve in his biceps two years ago.

After attacking his rehab as doggedly as he assails defenses, Denver’s 37-year-old quarterback is making it hard to fathom and easy to forget that not so long ago he was missing an entire season and getting fired in Indianapolis.

Manning, a four-time MVP, is off to the best start of his storied 16-year career.

Driven by last year’s playoff pratfall, Manning is putting up historic numbers while directing an imaginative offense that’s still working through growing pains.

Here’s the scary part for opponents: Even with so many footballs slipping through his teammates’ hands or going through the uprights after stalled drives, the Broncos (3-0) are averaging 42 points.

“I think Peyton’s playing at an all-time (high) right now,” said Philadelphia Coach Chip Kelly, whose Eagles (1-2) visit Denver on Sunday. “You couple him being at the top of his game and then give him the weapons that he has, it’s a pretty dangerous formula to go against.”

The 2013 Rocky Mountain version of the “Fearsome Foursome” is Demaryius Thomas, Eric Decker, Wes Welker and Julius Thomas, who have collected 72 catches for 943 yards and 11 TDs.

“Usually you have a main guy as part of the offense, a star that you can load up and take him away,” Eagles defensive coordinator Bill Davis said. “Peyton makes you defend the field.”

Manning is the first quarterback in NFL history to collect 12 touchdown throws in the first three weeks of the season, and his off-the-charts passer rating of 134.7 is way above the career high of 121.1 he set in his pinnacle 2004 season, when he threw for 49 TDs.

Manning was masterful Monday night in completing a career-high 86.5 percent of his passes in Denver’s wipeout of Oakland.

But Manning finds no time in his no-nonsense schedule to contemplate just how special this start is.

“This is a new season. It’s one week at a time,” he said. “I don’t have a great comparison to other years, but guys are making good plays in the passing game and we are doing a good job getting yards after the catch.”

Take Decker’s 61-yard gain Monday night. He runs an 18-yard curl and there’s a 6-inch window for Manning, who delivers a frozen rope of a throw that seems to stun even Decker, who hesitates for a split second before turning upfield.

“I was on him like a shadow,” Raiders cornerback Mike Jenkins said. “I actually felt the ball go across my fingers. (Manning is) a genius.”

Just imagine him in his prime? Are you kidding? In many ways it’s right here, right now.

Manning’s work ethic keeps him in tiptop shape and his mental mastery of the game keeps getting better.

“I’d like to think that any player would use the experience from the year before to his advantage, to learn what to do against certain defenses, to learn what not to do,” Manning said. “With being able to play a lot, you certainly gain great experience.”

He’s also putting that to use like never before.

“The guy is just awesome,” Jenkins said. “I’ve never seen anything like him. It’s very frustrating for you to be in the right spot and he still squeezes the ball in for a great throw. There’s not too much you can do about that. Most games you play, that’s your ball. But it’s Peyton Manning.”

Or Peyton Manning 2.0.

He bounced back last year from a series of neck injuries and surgeries that sidelined him in 2011, an all-too-familiar ordeal for the first family of football after his older brother, Cooper, saw his football dreams dashed because of a spinal condition.

The family patriarch, Archie Manning, said Peyton “never took football for granted because of what happened to Cooper.”

“I think he always knew he was fortunate in regard to health, but he wasn’t ready for his career to be over, not like that. Not four surgeries and having to leave the place where he had been so long. He just didn’t want it to end right there,” Archie Manning said.

“So I think the good Lord looked down on him there and allowed him to play some more football, so we are grateful for that.”