SAN FRANCISCO (CBS SF) – The 49ers will be without the face of the defense for the stretch run after news broke Tuesday that linebacker Patrick Willis will not play another snap for the 49ers this season.

The NFL sent out a tweet about the news Tuesday morning.

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Willis, considered among the league’s best defensive players over the last decade, hasn’t appeared in a game since injuring his toe in Week 6 against the St. Louis Rams.

The six-time All-Pro selection is the quarterback of the defense and is a serious loss as the team tries to climb out of third place and into the playoffs. The 49ers are 5-4 after defeating the New Orleans Saints in overtime Sunday. The team still has to play, among other teams, the first-place Arizona Cardinals, San Diego Chargers and defending NFC Champion Seattle Seahawks twice. The team can likely afford only two to three games in their final seven to have a shot at a playoff spot.

Willis and teammate NaVorro Bowman are considered by many the league’s most feared linebacker duo, but the team has been forced to play without either Pro Bowler in recent weeks. Bowman injured his knee at the end of last season.

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Rookie Chris Borland from Wisconsin, who has excelled so far in two starts, will continue to play the bulk of Willis’ snaps. In his last two games Borland has 35 tackles, including 18 tackles against the Rams on November 2 which were the most in the NFL this season.