Right at the cap would mean no room to resign any players before the offseason though, which is why the Packers usually keep a good amount of cap space available. Besides, I'll disagree with you in that I'd trade the two rosters for each other, especially not on the offensive side of the ball.
The two main stats I'm looking at for defense are:
Pts. game: Packers 18th 23.9 points Broncos 23rd 25.5 points
Total yards: Packers 18th 350.9 yards Broncos 23rd 371.8 yards
Anyway, my main point in bringing up Denver is that I don't think any team can do very well after depending on a star QB and losing him to injury. Manning and Rodgers are the main reasons the two teams are so good, when they play of course. Very few teams are able to build a great offense and a great defense at the same time and I think it's mostly due to cap constraints. It does happen, but it's not common and an unrealistic expectation. When Rodgers plays, an average defense is certainly good enough to win. They did go 15-1 with a historically bad defense a few years ago.
Gross numbers like total yards and total points are misleading. I don't think that requires any explanation.
I think Rodgers would do just fine with Jackson, Spiller, Choice, Johnson, Graham, the two very good rookies (Woods and Goodwin) and Chandler and a somewhat better offensive line. The Bills defense is very good; outstanding, in fact, when the offense can spend some time on the field. They've been a playoff caliber team when the rookie QB has been on the field once he got his feet wet with a couple of starts; in fact I would not rule them out of the second wild card just yet.
As of September, the Packers were right at the 2013 cap number of about $123 mil. They had a $10 mil cushion because of unused cap roll-overs. That cushion has gone down slightly with minor signings as other players have moved to IR. The cushion carries over to next season.
However, Rodgers' and Matthews' cap hits go up an aggregate $10 mil next year sucking up that cushion; that's the reason we're carrying the cushion, not for extensions. Next year's cap, excluding carryover, is expected to be flat.
The rumored $8 mil per year offer to Raji would have no impact on 2014 cap space if that's the way it goes down...it might actually result in a reduced Raji cap hit for 2014 vs. 2013. Raji's cap number for this year is about $6.6 million. The new deal would likely have a large signing bonus (as all big second contracts do), pushing the cap hit to the out years of the contract. Of course paying Raji anything like that kind of money would represent poor value.
Current dead cap is low at about $2.5 million, so there won't be any big windfall associated with dead cap rolling off (about a $1 mil windfall).
The Packer's current projected cap hit for the top 51 players now under contract for 2014 is about $107 mil, $10 mil more than the Bills. Ralph Wilson is one of the owners who actually has to pay attention to cash spending, not just cap. When a small market owner with a bare bones outdoor stadium in the snow belt buys his team's tickets to prevent blackouts, positive cash flow is hard to come by. On balance, excluding the QB position, the Bills have a better and cheaper team.
That $107 mil Packer figure includes nothing for the draft class, and nothing for guys going into FA...Raji, Shields, James Jones, Pickett, Finley, EDS and a few other lesser lights like Kuhn and Wilson. Did I miss anybody? There's not much cap slack going into next season if the Packers intend to keep these players.
Cutting Tramon Williams would kick in about $7.5 mil in cap space. His cap number for next season is $9.5 mil (ouch!) with a dead cap number of $2 mil. This is what happens with these back loaded second contracts. He'll be released or renegotiated down...Woodson redux.
The cap picture is not that rosy. If Raji sticks to his guns (fingers crossed!) and Finley goes unsigned (likely with the nature of this injury), then we'll have some serious cap slack to enter the FA market once again...for a Raji replacement or a safety.
Coincidentally, TT's significant FA signings in the past were for a DT (Pickett) and a DB (Woodson). I think it's time to once again go outside for an impact player.