Dumervil was hurt in a one-on-one pass rush drill during practice at the Broncos' training camp earlier this week, the team said on their website (http://www.denverbroncos.com/).
"It is in the pectoral area of his chest," Broncos coach Josh McDaniels told reporters. "No schedule or no determination in terms of the course of treatment, none of those decisions have been made."
Dumervil likely will have surgery and could return to the team in November, according to a report in the Denver Post that also said he could miss the season (www.denverpost.com).
The 26-year-old Pro Bowl linebacker led the NFL with 17 sacks last season. He signed a five-year contract extension last month that will pay him $58.3 million with $43.1 million guaranteed.
(Writing by Gene Cherry in Raleigh, North Carolina; Editing by Frank Pingue)