49ers' defensive coordinator says NaVorro Bowman may not play this season

San Francisco 49ers linebacker NaVorro Bowman is continuing to work his way back from a torn ACL and MCL suffered in last season's NFC Championship game, but it appears the rehab process could go longer than expected.

As defensive coordinator Vic Fangio conceded Thursday, it's possible that Bowman won't be able to play at all this season, according to CSN Bay Area's Matt Maiocco.

There is no timetable for the star linebacker's return, but the 49ers must declare him available to practice by Tuesday, or he will be forced to remain on the Physically Unable to Perform list for the entire season.

Having already lost Patrick Willis for the year with a toe injury, going without Bowman as well would be a significant blow to the 49ers' chances of making a run down the stretch.

The defense has performed well in their absences, but the linebackers' return would have had the potential to put the unit over the top heading into the playoffs.