The injury confirmed by two sources is a blow to the Patriots who pulled out a last-second victory over New Orleans on Sunday but may have lost four key players for significant time.

Mayo's injury is particularly difficult because he is the team's leading tackler with 55 total and 35 solo tackles and the Patriots seem to have a much thinner margin of error this season than in recent years.

He went down in the second half of Sunday's game and multiple Boston-area media outlets reported he was wearing a sling.

In addition to Mayo New England lost wide receiver Danny Amendola and guard Dan Connolly to head injuries on Sunday. Cornerback Aqib Talib hurt his leg and left and came back to the game. The Patriots are also dealing with a daily drama involving tight end Rob Gronkowski who has practiced but has yet to play this season after several surgeries on a fractured forearm.