The struggling Chicago Bears got another headache this week: Wide receiver Brandon Marshall got into an argument on Twitter with a Detroit fan and challenged him to a boxing match for charity.

Marshall said they should fight for $5,000 but the fan upped it to $25,000. The fan seemed to back off and Marshall later took down Thursday's tweets.

"Everybody wants to hide behind their words," Marshall said Friday. "Even sometimes the media wants to hide behind their words and think that they're tough guys. This is an opportunity for him to do something nice for some kids. But also back up his words."

The idea didn't sit well with Bears executives, who gave Marshall a three-year contract extension for $30 million this year.

Marshall said he was approached by team general manager Phil Emery in the hall and said Emery told him his contract limits potentially dangerous off-field activities.

Marshall said Emery also told him a boxer has callouses, which could be a possible danger to a wide receiver trying to catch passes. Marshall said he told Emery he already has them because he uses boxing to aid his cardiovascular training.

"That quieted him up pretty good," Marshall said. "I like boxing. I like it, so I do it. It's a great workout. It's great for cardio."

Coach Marc Trestman attempted downplay the incident.

"I don't want to make this anything more than what it was -- it was a response on social media," he said. "It wasn't anybody's preparation or anybody's work ethic out on the football field."

Trestman did say the situation would be addressed with Marshall.

"We don't police everything that they do," Trestman said. "We ask them to take a deep breath before they press that send button. Hopefully they make decisions that are in the best interest of their team. But we're not perfect. None of us are."

The Bears (3-6) are in last place in the NFC North. Asked if the incident could distract him from Sunday's game against Minnesota (4-5), Marshall said it wouldn't, but added: "Life outside of the locker room must go on."