ENGLEWOOD, Colo. -- The Denver Broncos' quarterback camp opened Monday with Brandon Marshall running routes but catching no passes and Travis Henry out the first week with a pulled hamstring.

The Broncos feared that Marshall would miss the start of training camp in July after cutting an artery, a vein, a nerve, two tendons and three muscles in his right arm in an accident in March at a resort in Orlando, Fla.

"June 22 will be his first day he's able to catch the football, which gives us plenty of time before we start our summer ball," coach Mike Shanahan said.

Travis is expected back next Tuesday after pulling a hamstring during 100-yard drills Friday.

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Story: Broncos Training Camp Begins

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Marshall is key with Javon Walker out at wide receiver. Denver brought in some experience, signing Keary Colbert, Sami Parker and Darrell Jackson to play opposite Marshall.

"Anytime you lose a guy like Javon Walker like we did, you want to bring in some people you feel that can compete right away, some guys that have some experience," Shanahan said. "You never have enough depth at that position. Hopefully we have more depth this year than we've had."

On defense, Boss Bailey had been counting on his brother to get acquainted with the rest of the Broncos, but Champ Bailey looked around and saw plenty of unfamiliar faces.

"It's funny because I'm asking Champ who everybody is and he's saying, 'I don't know.' Everybody's learning everybody, a lot of new faces around here, so I blend in pretty good," Boss Bailey said.

The Broncos have turned over nearly half their roster, including saying goodbye to linebacker Ian Gold (released), offensive lineman Matt Lepsis (retired) and Walker (released). In their place the Broncos drafted nine players and signed seven college free agents to go along with experienced players, namely free-agent linebacker Boss Bailey and defensive tackle Dewayne Robertson.

"I said every year a third of your team changes, and this year it's 40 percent," Denver head coach Mike Shanahan said. "An extra 7 percent, but that's typical in the National Football League with free agency and the draft, there's going to be changes.

The hope is the new faces are going to help the Broncos get back to the postseason for the first time in three seasons. In 2007, Denver started out 2-0 but finished 7-9.

"First of all, we weren't very good at the end of the season," Shanahan said. "Both offensively, defensively and special teams we were pretty average. What you always try to do is improve your football team. We brought in 20 free agents that we thought these guys would help improve our football team."

The players knew changes were needed.

"Coaches felt like they made moves to help this team," defensive back Dre Bly said. "Last year was totally unacceptable. Last year we didn't show how good of a team we could be week in and week out. We weren't as consistent as we should have been."

The changes weren't just with the players. Defensive coordinator/defensive backs coach Bob Slowik took is leading the defense this year, replacing Jim Bates, and it's a change Bly feels will make the defense better.

"He was a guy we had a lot of respect for in the defensive backs room," Bly said of Slowik. "It gives us something to look forward to. We're not going to make many changes, just a few, in terminology."

Notes:@ Shanahan said center Ben Hamilton (post-concussion symptoms) has practiced but hasn't taken any contact to his head.