In a story published Monday, Marshall told the Rocky Mountain News he had slipped on a fast-food bag while vacationing at a resort with his mother, father and siblings. He said there was nothing more to read into it than that and described his injury as "a little cut on my arm."
He repeated the explanation in an interview on satellite radio Monday.
The NFL Network reported Monday night, citing no sources, Marshall had severed an artery, a vein and a nerve in his forearm along with tendons to five muscles.
The NFL Network also reported Marshall told the team he was wrestling with family members when he got hurt.
Marshall underwent surgery on Saturday and will be in a cast for two weeks, then a splint for a month, the NFL Network reported, but he will be ready for training camp.
Neither Marshall nor his agent, Fletcher Smith, returned a phone message from The Associated Press. Marshall was at Broncos headquarters Monday, when the team's offseason strength and conditioning program got under way, but did not speak to reporters.
Team spokesman Jim Saccomano said Monday night that he had no information on Marshall's injury.
Also on Monday, a jury trial was postponed for Marshall, who is accused of driving under the influence. A new trial date was set for June in Denver District Court after his lawyer asked for a delay.
Marshall was arrested in downtown Denver on suspicion of drunken driving on Oct. 22, hours after he caught six passes for 77 yards in the Broncos' 31-28 victory over the Pittsburgh Steelers at Invesco Field.
Marshall blossomed into the Broncos' best receiver last year, catching 102 passes for 1,325 yards and seven touchdowns.