Since Belichick became head coach of the NE Patriots, Dallas has played them 6 times and has a 1-5 record. Perhaps you'll chalk that up purely to having Tom Brady at QB, but Belichick at coach cannot be underestimated.
I wouldn't be surprised to see Belichick do two things just to pour salt in Dallas' wound and to get a last laugh on a former player:
1. Exploit the weak Dallas run defense using an ex-Cowboy RB Zeke Elliott 25-30 times. (insert Belichick grin)
2. Exploit a Dallas pass defense still trying to reestablish itself by picking on ex-Patriot CB Stephon Gilmore. (insert Belichick grin)
*I don't see Micah Parsons being a big factor. Belichick will have the Mac Jones getting that ball out in 2 seconds or less, and he'll have Zeke and the running game running right at Parsons. Gonna be an ugly game.