Denver Broncos quarterback Peyton Manning has revealed that he has still not fully recovered from his neck surgery in 2011.

Manning missed the entire 2011 campaign after undergoing spinal fusion surgery during the off-season, a procedure that many thought could spell the end of his illustrious NFL career.

However, he has experienced a revival since joining the Broncos in 2012, throwing 92 touchdown passes in his two seasons with the team and winning his record fifth NFL MVP award last year.

Despite his impressive performances in Denver, though, the 38-year-old insists that he is still not 100% compared to his pre-surgery performances.

"I'm not at a 100% compared to what I was before my surgery, but I have made strides each season and this year felt a lot better than I did the year before. These nerves just go at their own pace," Manning said on the Late Show with David Letterman.

"You talk about waking up every day at 7am excited and then being pretty depressed by noon every day - today's not the day."

Manning led the Broncos to the Super Bowl last season only to be beaten convincingly by the Seattle Seahawks.