The effectiveness of Peyton Manning returning to the NFL after multiple neck surgeries is one of the NFL's biggest questions entering the season.

ESPN's Ron Jaworski watched preseason film of Manning as he returns from injury with the Broncos.

"I was wowed by his performance," wrote Jaworski. "As odd as it may sound, and despite all of the obstacles, in terms of pure performance what I saw was a quarterback in his prime."

Manning was particularly impressive against the 49ers.

"As the preseason progressed, Manning's arm strength and velocity appeared to improve," wrote Jaworski. "Moreover, his accuracy and mental approach seem to be as sharp as ever, despite the transition to the new team. It's already clear that the Denver offense is in his mold and features a lot of the same formations and route combinations he utilized in Indianapolis. He's already back, doing his dance behind center, putting people where he wants them.