With a crazy, shortened free agent period beginning 72 hours after the lockout is lifted, some teams are certain to look very different in a couple of weeks. There are a lot of variables involved in an NFL season, and anything can happen, but I expect a few teams to be much improved in 2011.

The passing game is the main driver in the modern NFL and just looking at the spread between each team’s passer on offense, versus what they allow on defense, tells a lot about a team.

Looking back at the 2010 season, every team that had a better passer rating on offense than they allowed on defense had a winning record, and only one team (the Jets) surrendered a higher passer rating (77.1) than their offense produced (76.5). A few teams underachieved based on that spread in 2010 and it might be a key to their quick turnaround in 2011.

Not all of these teams are going to the playoffs, but they’re certain to improve in the win column.

Cowboys — They dropped from 11 wins in 2009 to six in 2010, and it wasn’t all Wade Phillips’s fault. The return of Tony Romo might seem like an obvious help, but Jon Kitna was very good as his replacement. It’s their suspect pass defense that hurt them last year. There’s no guarantee it will be any better, but if the secondary can play like it’s 2009 again, they could easily be three wins better.

Broncos — They’re in a similar situation as the Cowboys: their defense was solid in 2009 and abysmal in 2010. There’s only so much a coach can do on defense with the players he’s given, but new head coach John Fox always had a solid defense in Carolina and he can certainly make them better. Also, if they stick with the underrated duo of Kyle Orton to Brandon Lloyd (instead of Tim Tebow) they have a dynamic pass offense. It’s a lot easier to improve your win total when you only won four in 2010, and they too could easily see a three-win improvement.

Bills — Their team passer rating improved to the mid-70s in 2010 just by starting Ryan Fitzpatrick (81.8 rating). But their pass defense, which was one of the best in the league in 2009, fell apart in 2010. They’re another team — if their defense bounces back to its level of play from 2009 — that could improve at least by three wins from their awful 2010 total of four.

Panthers — When you only win two games in a season, you’ve got no where to go but up. As a team, their quarterbacks combined for a passer rating below 60. I’m not a believer in Cam Newton, but if he can at least prove competent as a rookie, and produce a quarterback rating between 70-75, he could turn them into a seven-win team. If he did, a five-win improvement would probably be the biggest jump in the NFL.