A lot has changed.
1. The two major deficiencies from AFCCG - demolished OL and virtually non-existent running game - are now surprisingly the strength of the team - and both amongst top in the league. This reason alone should be enough to base a lot of optimism on returning to MH.
Here's a nice comparison in Reiss article:
Stronger run game has Patriots better prepped to handle Denver challenge
2. One could argue that the offence is weaker this time with no Gronk but that's not necessarily the case. Firstly, well balanced offence is much more important (and productive) asset than any single star player even if it is called Gronk (btw - Brady was 27/56 w 2 INT). Second, without the running game play-action against a D like Denver is virtually impossible as well and short passing game much more difficult. Third, the passing offence alone proved itself against the top D Monday night.
It was basically Brady and Gronk vs Denver D in the 4th quarter comeback attempt. Without Gronk Denver D will have to pay attention to a “plethora“ of weapons all over the field that proved to be very productive and versatile - and that should be more difficult to defend.
3. Pats D has more depth (strong rotation in all front 7 positions), possibly more versatility as well as witnessed Monday. And is stronger against the run .. with Denver running game virtually non-existent after CJ Anderson and Janovich went on IR.
4. Last but not least - the hot Pats D with thousand faces will go against rookie QB instead of someone named Payton Manning. Even if Manning was in decline and hurt his experience was there to recognise what Patricia is throwing at him. It is reasonable to believe rookie Siemian will have more truble deciphering whats going on in front of him.
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On the other side Denver lost some depth and a little bit of the edge as well on D in the offseason with some important FAs leaving. There are some injury concerns with both starting ILBs Marshall and Davis. Talib and Harris are not 100% as well.
On offense the running game as mentioned is virtually gone, OL has struggles all year and actually Sanders and Thomas are doing wonders to keep this offence going at all.
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Bottom line: Broncos still play as tough as anyone and they are monsters on their home field .. but they have many shortcomings at the moment and they need a perfect game to upset Pats.
The only liability the Pats have is the punt return game. Ironically - they will probably have a lot of work returning Denver punts. They have good PR options on the team but possibly too valuable to use them (Edelman, Lewis, White) - though that might change on Sunday.