The muscle is expected to take at least four months to heal, meaning Dumervil, who led the NFL with a Broncos-record 17 sacks last season, could miss the entire 2010 campaign. The injury typically requires surgery, which The Denver Post reported Dumervil likely will have.
"We're not sure exactly the timetable that we're talking about," McDaniels said, according to The Post. "So we're not going to look at it as the glass is half empty, we're going to look at it the other direction. And hopefully we'll have him back at some point. But we have a lot of players in the locker room that I know are going to have to combine their efforts to try and do some things that certainly he was responsible for while he is gone."
The Broncos won't rush to place Dumervil on season-ending injured reserve, pending a second medical opinion on his injury, and could carry him on their roster for a while, La Canfora's source said. If the Broncos fell out of the playoff race, they could shut down Dumervil for the season, the source added.
Dumervil was hurt at practice Wednesday night during a 1-on-1 passing drill and walked off the field clutching his right arm. The Broncos described the injury as to the "pectoral area of his chest."
Dumervil, 26, parlayed his breakout 2009 season into a five-year, $58.332 million contract extension that included $43.168 million in guarantees against injury -- a record for a player at his position.
"Nobody is going to replace him as an individual," McDaniels said. "We know that. We're not going to try to do that. So with that being said, this is just another adversity I think that as a team, as an organization you have to face.
"You have to move on, move forward and try to play good football. We're not going to be the only team that this happens to this year. We don't feel sorry for ourselves. I know Elvis is going to work as hard as he can once we determine how we are going to treat it."
The other outside linebackers, former first-round draft picks Robert Ayers and Jarvis Moss, didn't have a sack last season. Mario Haggan played on the other side of Dumervil in '09.
The Broncos will stick to their 3-4 scheme, but they are considering sprinkling in some of their old 4-3 alignments.
McDaniels beefed up his defensive line through free agency, and the centerpiece of that project, nose tackle Jamal Williams, practiced Thursday for the first time since camp started.
The 348-pound Williams, who spent his first 12 seasons with the AFC West rival San Diego Chargers, was brought in to be a run-stuffer and help push the pocket, allowing players such as Dumervil to apply more pressure to the quarterback.
"We're not going to change the style of defense that we have," McDaniels said. "There might be a bigger body out on the edge sometimes. It may take a few people, may take some creativity for us."
On Thursday, the team placed wide receiver Kenny McKinley (knee) and safety Josh Barrett (shoulder) on injured reserve, ending their seasons.
The Broncos lost their top two tailbacks, Correll Buckhalter (back) and Knowshon Moreno (hamstring), on the first day of camp. Moreno likely will miss the rest of camp, and Buckhalter is expected back next week.
Inside linebacker D.J. Williams and safety Brian Dawkins have missed practice time, too. No reasons have been given for their absences.
Denver already was without All-Pro left tackle Ryan Clady as he recovers from a torn left patellar tendon that he suffered while playing basketball during the offseason.
All these standouts going down reminds McDaniels of the 2008 season, when he was the New England Patriots' offensive coordinator and quarterback Tom Brady was lost for the season with a knee injury in the opener.
"Anytime you lose a player for a period of time that has that kind of impact on your team, nobody looks forward to that," McDaniels said. "But they're not going to write at the end of the season, 'Our record was such and such and Elvis Dumervil had an injury in training camp.' They're just going to tell you what our record was. We're not going to sit here and feel sorry for ourselves."
Just when the Broncos received backfield reinforcement with the signing of free agent and Denver native LenDale White on Wednesday, their All-Pro outside linebacker was hurt.
Dumervil prospered last season in the Broncos' new defensive look that converted him from a classic 4-3 defensive end into a stand-up outside linebacker in the 3-4, which employs three down linemen and four linebackers.
Despite his diminutive stature -- 5-foot-11 and 248 pounds -- Dumervil's extraordinarily long arms and low center of gravity make him difficult to defend as he has built-in leverage against almost anybody he faces. He has 43 sacks since being drafted in the fourth round out of Louisville in 2006.
Dumervil was anticipating another big season, too, joking around before camp began about the pressures of trying to defend his sacks crown.
"We all feel bad, obviously, for Elvis," McDaniels said. "I know how badly he wanted to start the season."
The Associated Press contributed to this report.