If the Patriots and Bengals end up with the same record, it will come down to strength of victory.
At the moment the Patriots victory opponents combined record is 65-85 and the Bengals is 60-89 (Bengals one game less as the Bears play tonight).
It is possible for both the Patriots and Bengals to both win and then all the Bengals strength of victory opponents to win and the Bengals could beat the Pats to the 3rd seed. Unlikely, but possible the same for both teams losing.
Pats strength of victory teams: Buf 5-10 (x2), Atl 8-7, Bal 8-7, Ten 7-8, TB 3-12, Mia 7-8, NYJ 8-7, Car 7-8, Jax 7-8.
Bengals strength of victory teams: GB 10-5, Pit 8-7 (x2), Cle 4-11 (x2), Bal 8-7 (x2), Chi 5-9 (still to play Min tonight), Det 2-13, KC 3-12.
Atlanta play Tampa Bay in Week 17 so the Pats will have 1 definite win added and so will the Bengals as Detroit plays Chicago.
Phew!