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Updates From Monday, Jan. 13:

Ian Rapoport via the NFL Around the League Twitter feed reports the latest information regarding Brandon Spikes injured PCL:

Rapoport added:

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Updates From Saturday, Jan. 11:

According to a report from ESPN's Chris Mortensen, it wasn't just the knee that landed Spikes on the IR:

Michael David Smith of Pro Football Talk reports that the trip to the IR was a compromise:

Placing Spikes on injured reserve serves as something of a compromise: For Spikes, it allows him to collect his playoff pay, which he wouldn’t receive if the Patriots had cut him for showing up late to work. For the Patriots, it ensured that Spikes wouldn’t get picked up right away by the Colts, Broncos or Chargers.

Jeff Howe of the Boston Herald reports that Spikes may not be headed to the IR, despite reports to the contrary:

A source today called a report that Patriots linebacker Brandon Spikes was placed on injured reserve on Monday due to him being late to a meeting "absolutely untrue and unfouned." ESPN reported that Patriots coach Bill Belichick made the move as a "final straw" after Spikes was reportedly late to a meeting last Friday. This much is known: Spikes was placed on injured reserve Monday because his knee had become too much of a burden over the second half of the season, and all parties involved knew it was time to shut it down. The decision was mutual, and there was no disagreement from Spikes, as much as he hated to see his season come to an end in the playoffs. There are currently no plans for Spikes to undergo surgery, though he is traveling to the Kerlan-Jobe Clinic in Los Angeles for a second opinion to verify that. Rest will heal the injury.

However, NFL Network's Ian Rapoport reports that rumors of Spikes' IR trip being practice related aren't accurate:

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The New England Patriots will be without third-leading tackler Brandon Spikes during their 2014 NFL playoff run after the linebacker was placed on the season-ending injured reserve list with a knee injury, according to ESPN NFL Nation reporter Mike Reiss:

The announcement came on Monday, Jan. 6, less than a week before New England's AFC divisional playoff clash with the Indianapolis Colts.

While losing Spikes for the season is a huge blow to New England's already short-handed defense, it doesn't squash the Patriots' Super Bowl aspirations. After all, the Pats still boast arguably the greatest coach and quarterback tandem in NFL history with Bill Belichick and Tom Brady. Together, they have won three Super Bowl titles.

And while New England's defense bent throughout the regular season, ranking 26th in yards allowed, it never broke, ranking 10th in scoring defense (21.1 points per game allowed).

Still, the Pats will miss Spikes' team-leading eight tackles for a loss and his experience in the middle of the linebacker corps. Spikes' absence will make the middle of the defense a target for the Colts, as the interior has taken a big hit through the course of the season, as Ian Rapoport of NFL.com notes:

The former Florida Gators star has played in six postseason games with the Patriots in his career. He played in all three of their postseason games in 2012, a run that concluded with a loss to the New York Giants in Super Bowl XLVI.