It's very likely that he was out of position on that play, but it should be noted that the Bills ran a read option on that play. It's possible, but not likely, that Briggs' responsibility on the was to tackle the QB, which he was heading into position to do. If that's so, other players have the RB responsibility on read option. Again, unlikely, but it's hard to cherry pick plays to show guys out of position without knowing how they were trying to defend the play as an entire unit.