ENGLEWOOD, Colo. -- Denver Broncos wide receiver Wes Welker returned to the practice field Monday as he continues through the NFL's concussion protocol.

Broncos receiver Wes Welker has suffered three concussions since Nov. 17. AP Photo/Jack Dempsey

Welker has not been cleared for contact and is still a question mark for Sunday night's regular-season opener against the Indianapolis Colts. But Monday's appearance on the practice field -- the Broncos practiced in jerseys, shorts and helmets without pads -- was his first since he suffered a concussion Aug. 23.

"He's still in the protocol. He's still exercising. Feel good about progress," Broncos coach John Fox said after Monday's practice. "... But obviously, as I said all last week, he's a guy we'll be cautious with, and our main concern is his safety."

It marked another stage in Welker's recovery from what was his third concussion since Nov. 17. He had been cleared to travel with the team last week to Texas for the preseason finale against the Dallas Cowboys. Welker ran some routes in shorts and a T-shirt with no helmet before that game, but he was not in uniform once it began.

John Elway, the team's executive vice president of football operations and general manager, said Saturday that Welker was making progress but the team would "take it one day at a time."

Welker still has benchmarks to meet within the protocol before he can return to full participation in practice or play in a game.

The timetable for a player to return begins when he is symptom-free, and if Welker reaches one benchmark within the protocol without any symptoms, he advances to the next step.

If Welker remains symptom-free after Monday's work -- Tuesday is an off day for the players -- he could progress to the next benchmark, which would be full participation in all parts of practice.

To return to play, Welker would have to be cleared by an independent physician designated by both the NFL and NFL Players Association.