NFL Media's Albert Breer reports that Ridley will undergo an MRI on Monday, but there is concern that he tore his ACL.
Per NFL Media Insider Ian Rapoport, via sources informed of the situation, Mayo is believed to have suffered a "significant" knee injury and will have more tests Monday. The linebacker, who has led the Patriots in tackles in five of the last six seasons, immediately knew he was seriously hurt. Mayo's teammates took off their helmets and kneeled by him.
Mayo is one of the tougher players for the Patriots to replace because he's a leader and defensive signal-caller. New England also isn't very deep at linebacker after losing Brandon Spikes in the offseason. Chris White and safety Tavon Wilson helped to take some of Mayo's snaps Sunday. It would not be a surprise if those same Patriots are filling in for Mayo for a while.
Ridley is the best pure runner on the Patriots and adds an element of toughness between the tackles that Shane Vereen simply doesn't bring to the table. Brandon Bolden stepped in to take some snaps in Ridley's place. Meanwhile, guard Dan Connolly had a head injury and was downgraded to out, meaning that New England's beleaguered offensive line has to make another change.
UPDATE: On WEEI on Monday afternoon, Belichick said that "it doesn't look too good" for Mayo and Ridley.