Marshall, who has brooded since demanding a trade and asking for a new contract, was informed of the suspension by McDaniels on Friday.
"We tried to handle this situation with Brandon as privately and professionally as we could throughout the entire process with he and his agent, Kennard McGuire," McDaniels said at a news conference. "This morning, we made the decision as an organization to go ahead and suspend Brandon and that suspension will last through Sept. 5th. We'll look forward to having him back on Sept. 6th as we begin our preparations for Cincinnati" in the Sept. 13 regular-season opener.
McGuire didn't immediately return a phone call Friday to The Associated Press, and was said to be out of the country until Monday.
McDaniels did not single out a specific episode, but said the suspension resulted from a series of incidents, though some boorish antics during the team's practice Wednesday -- after Marshall had been warned about such conduct that very morning -- seemed to be the final straw for the coach.
"His actions didn't really change after that warning. That leads us to today," McDaniels said.
Marshall went out during pre-practice warm-ups and walked while the rest of the team ran. He punted a ball away instead of handing it to a ball boy, and swatted a pass thrown to him. His actions were caught on video and broadcast by KMGH-TV.
The Broncos already have had discussions with the league regarding Marshall's suspension. They are expected to reassess the situation when the preseason ends Sept. 5.
Marshall said during an ESPN interview Thursday night that he was not trying to force a trade through insubordination, but that frustration got the best of him during a disruptive display at practice this week.
Marshall said some of the video, which included a shot of him sitting on his pads before practice, was taken out of context. But he acknowledged his frustration boiled over and that it was an error in judgment to act as he did, especially when he punted the ball.
"I think everybody knows there's a lot of stuff built up there,
and me handling it that way wasn't good," Marshall said.
Marshall said he wasn't trying to force his way out of town -- he
asked for a trade this summer after the Broncos declined to rework
a contract that will pay him $2.2 million this season.
"I'm not out there trying to be a distraction to the team,"
Marshall said. "Unfortunately, yesterday I kind of let my
frustration get the best of me."
The receiver was held out of practice Thursday, apparently as the organization was formulating its disciplinary response.
"We're trying to handle this in a way that we can discourage this from happening," McDaniels said. "We didn't want to be in this situation. We never wanted it to get to this point. I'm sure they didn't either."
Fellow wide receiver Brandon Stokley said he wasn't surprised the Broncos temporarily banished Marshall.
"Not really, not with his attitude and how he was acting," Stokley said. "Something had to be done. They made the decision. We're moving on, and hopefully in a few weeks, when he's back, he'll be ready to contribute."
Daniel Graham was concerned enough about Marshall's behavior at practice that the tight end said he talked to him about it several times. He said his main concern now is to make sure it doesn't become a distraction to the team.
"We've had a few conversations and Brandon, he's running his own ship," Graham said. "He's doing what he feels is best for him. Now, I'm just making sure, as a leader on this team, that we stay focused."
For all of the tension and disagreement between the receiver and his coach and organization, McDaniels said he hasn't given up on the notion that the sides can work things out.
"I'm not sure necessarily if I think it will or I think it won't [work out]," McDaniels said. "I'm just hopeful that it will, because obviously he's a talented football player that we'd love to have pulling in the same direction as the other 79 guys that go out there and work their tail off.
"Obviously, there's a disagreement about some things. We're trying to make it right, to work through it."
Marshall was held out of the Broncos' preseason game Sunday night at Seattle after admitting he didn't know the playbook and
running almost strictly with the scout team last week.
Marshall, who had 206 receptions the past two seasons, is also upset with what he believes was the team's misdiagnosis of a hip injury that required offseason surgery. He pulled a hamstring during the first weekend of training camp and didn't return until a week ago.
In addition, Marshall missed the team's exhibition opener against San Francisco two weeks ago because he was on trial in Atlanta, where he was acquitted of a misdemeanor battery charge. Prosecutors had accused him of beating his then-girlfriend.
Marshall hoped the acquittal would give him leverage for a new deal in Denver or elsewhere. He was angered when the Broncos prohibited teammates from saying they were happy for Marshall about the verdict.
That's when Marshall began spending more time between drills with the scout team and the defensive unit instead of his fellow offensive players.
The run-in with Marshall marks the second clash with a high-profile player since McDaniels, the former New England Patriots offensive coordinator, was hired in January to succeed the fired Mike Shanahan. McDaniels had a falling out with Pro Bowl quarterback Jay Cutler after he learned his new coach had discussed trading him in a foiled attempt to land former New England quarterback Matt Cassell, who is now with Kansas City.
Cutler subsequently forced a trade to the Chicago Bears, who are due in Sunday night, when the Broncos play their first home game under McDaniels.
McDaniels said his issues with Cutler and Marshall were nothing unusual, just part of being an NFL coach.
"We're not unique, we're not unique at all," McDaniels said. "Other coaches, other organizations have challenges in front of them and you deal with them as best you can."
Information from ESPN reporter Ed Werder, ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.