You don't have to look back too far to make a case for the impact an undrafted free agent can have. Arian Foster led the NFL in rushing last season, not long removed from waiting out draft day without having his named called.
But that's actually the beauty of the shorter NFL draft. There's a misconception that a shorter draft is less efficient, or a messier process, but it's the opposite. For years, when teams were routinely drafting a dozen players, you'd have guys drafted late, stuck in camp with a team, but with no real shot to stick. They'd get cut and have to start the free-agent process. But with a draft that goes only seven rounds, there are a number of guys who will have multiple offers, and can scan the depth charts and seek out the best situation to make a roster.
That's a good thing, because there are a lot of players who go undrafted that shouldn't have based on talent. Foster is a clear case. I had him as a likely third-round pick at one point, but in his final year at Tennessee he got tagged with the "fumbler" label by many teams and dropped on some boards. Good thing for the Texans.
Here's a ranking of undrafted free agents in terms of potential 2011 impact. It's not a talent scale -- it's about guys who have performed enough already to get the opportunity for major playing time.
1. Dane Sanzenbacher, WR, Chicago Bears
Whatever you do, don't peg Sanzenbacher with the "scrappy" label. He's not a total burner, but he's a safe mid-4.5 runner with a 33-inch vertical and enough athleticism to stack up with a lot of top receivers. Sanzenbacher has great hands, good quickness out of his breaks, and can run with the ball in his hands. He got more than 16 yards per catch in the preseason, and since he learned the X, Y and Z positions, Mike Martz could use him all over the place depending on where the holes emerge. He won't pile up numbers, but he'll work his way into the mix.