He was suspended for at least the rest of the regular season and postseason - if the Browns qualify - after Garrett swung an opponent's helmet and used it "as a weapon" by striking Pittsburgh quarterback Mason Rudolph in the head.

The violent outburst in the final seconds of Thursday's nationally televised game against the Steelers resulted in the longest suspension for a single on-field infraction in league history.

Tennessee's Albert Haynesworth was suspended five games in 2006.

The league's No.1 overall pick in 2017 was also fined an undisclosed amount, and Garrett must meet with Commissioner Roger Goodell before his reinstatement is considered.

Until then, the defensive end's career is on hold.

After wrestling Rudolph to the ground as the Browns were closing out a rare win over their rivals, Garrett ripped off the quarterback's helmet and clobbered him on top of the head, triggering a brawl that capped another physical game between the AFC North teams.

"I made a terrible mistake," Garrett said.

"I lost my cool and what I did was selfish and unacceptable. I know that we are all responsible for our actions and I can only prove my true character through my actions moving forward.

"I want to apologise to Mason Rudolph, my teammates, our entire organisation, our fans and to the NFL."

Rudolph, who suffered a concussion earlier this season, avoided serious injury and said after the game the attack was "cowardly and bush league".

The NFL said Garrett "violated unnecessary roughness and unsportsmanlike conduct rules, as well as fighting and removing an opponent's helmet and using it as a weapon".

Steelers center Maurkice Pouncey, who was trying to separate Garrett and Rudolph, was suspended three games without pay and also fined for punching and kicking Garrett.

Browns defensive tackle Larry Ogunjobi was suspended for one game. He shoved Rudolph to the ground from behind during the melee.

The Steelers and Browns were fined A$367,000 each.

Browns coach Freddie Kitchens met with Garrett at the team's training facility Friday and said the 23-year-old expressed more remorse.

"He understands that he let himself down, he let his teammates down and he let his organisation down," Kitchens said.

"We look at our team as a family, and in a family, sometimes family members make mistakes.

"We know who Myles is and the character that Myles has, and that is under no circumstance what he wants to be portrayed as. We will support him."

Australian Associated Press