New England Patriots linebacker Brandon Spikes was placed on season-ending injured reserve partly because he was late for practice last week, league sources told ESPN.

The Patriots placed Spikes on IR last Monday, a surprising move considering the linebacker played all 16 regular-season games despite being hobbled by a knee injury for much of the year.

Spikes was late for New England's bye week Friday practice, which was the final straw for Patriots coach Bill Belichick, who already had fined him for multiple incidents that the linebacker believed were practically explained, according to league sources.

Spikes took to Twitter on Friday, Jan. 3, to publicly appeal for help when his car apparently was stuck in the snow.

The Patriots and Spikes mutually agreed to the IR designation as opposed to an outright release, which would have made the linebacker available to the remaining playoff teams.

On Monday, Spikes' agent released a statement saying the decision was the Patriots' and theirs alone.

"The team's decision to place Brandon on Injured Reserve was not a mutual decision, nor need it be," Gary Uberstine said in the statement. "Brandon had every intention to keep playing throughout the playoffs, despite the pain he was experiencing throughout the season. We never had a single conversation with the Patriots in which they threatened to release him if he didn't accept the Injured Reserve designation."

The Patriots travel to face Peyton Manning and the Denver Broncos in Sunday's AFC Championship Game.

Spikes, who will be a free agent this offseason, will receive the Patriots' playoff shares this postseason before hitting the open market on March 11. Sources said the NFL Players Association accepted Spikes' decision not to file a grievance because the transaction worked to his advantage, based on the reasons stated -- playoff shares and the chance to get healed before free agency.

Spikes, 26, recorded 86 tackles -- the third-highest total on the team -- and one interception this season, his fourth with the Patriots.