Around this time every year, fans get bent out of shape hoping their favorite teams sign free agents. Some teams, like the Colts, stay away entirely. The reason is that free agency rarely produces solid players.
Why doesn't free agency pay off? Simple: restricted free agency and the franchise/transition tags. Essentially, if the team that drafted a player still wants that player, it's easy to keep him. The restricted tenders and the tags mean that a team rarely has to lose a player until it wants to. The quintessential example of this for the Colts was Edgerrin James. James became a free agent after the 2004 season. The Colts franchised him for a year, before cutting him lose. He signed a big deal with Arizona, but he was mostly used up and worn out by that time. He struggled behind a bad line, and never paid off the Cardinals for their multi-million dollar investment. If a player is a free agent in the NFL, it means his original team simply no longer thought he was worth the money. Add to that teams bidding against each other, and the result is rarely a payoff.
Some fans know this intellectually, but they don't realize just how grim the prospects of signing a good free agent really are. If you go back over the list of the top free agents for the past four seasons, it's telling. I've gone through every free top free agent who actually changed teams in that span, and the results should scare you off from free agency forever.
Of the top free agents, only 9 were of any real value to the teams that signed them:
Patrick Kerney (DE) had a Pro Bowl/All Pro season with Seattle, but was out of the league in 3 years
Matt Schaub (QB) was a restricted free agent, but changed teams thanks to a trade between the Falcons and Texans. Went to a Pro Bowl.
Eric Steinbach (G) has started 62 games for Cleveland.
Kevin Curtis (WR) had one decent season (1110 yards receiving). He is the ONLY unrestricted free agent WR to top 1,000 yards receiving since 2007.
Nate Clements (CB) has started 53 games at corner in San Fransisco
Leonard Davis (RG) switched from left tackle to right guard and has gone to 3 Pro Bowls in Dallas.
Joey Porter (LB) had a 17.5 sack season for the Dolphins and made one Pro Bowl
Ken Hamlin (S) has played 44 games for Dallas and made a Prow Bowl.
Deon Grant (S) started 48 games with 8 picks for Seattle
Wes Welker (WR) was a restricted free agent was traded to New England. He's gone to 3 Pro Bowls, and has been an All Pro.
Note: if a player started for a team at a position that can be measured statistically and didn't play well, I counted him as a bad signing. If he started a position that is difficult to quantify (like offensive guard), I counted him as a good signing as long as he started a significant number of games. In other words, this list is biased to make free agents look as good as possible. It's possible some of these 'good' signings were actually bad ones.
Of the top 24 players who changed teams, 10 of them provided any real value. 5 of those went to Pro Bowls, 2 became All Pros. However, 2 of the Pro Bowl players were restricted free agents, essentially traded not signed outright (Schaub and Welker). Also consider that teams that don't sign free agents and lose players get compensatory picks in the next draft (2008). Key players selected with those picks include Pro Bowl tackle Carl Nicks of the Saints and Pierre Garcon, as well as a handful of other starters around the league. These players come much cheaper than free agents.
There were 25 top free agents who changed teams. Only 7 produced any real value:
Jared Allen (DE) was franchised but traded to the Vikings. He has put up 2 Pro Bowl and 1 All Pro Seasons.
Asante Samuel (CB) went to Philly and has made three Pro Bowls.
Alan Faneca (G) went to the Jets for two seasons, making two Pro Bowls.
Justin Smith (DE) went to San Fransisco and made two Pro Bowls
Michael Turner (RB) went to Atlanta and made two Pro Bowls and 1 All Pro team.
Calvin Pace (DE) went to the Jets, has been a 3 year starter and had 20.5 sacks.
Jake Scott (G) went to the Titans and has been a three year starter.
None of the other free agents started as much as two full seasons Bernard Berrian of the Vikings did post 964 yards receiving one year.
So, of 25 top free agents, 7 were worth signing. 5 went to Pro Bowls, but one of those was a franchised player who went in a trade.
Of the top 25 players to change teams, 9 had any kind of impact.
Matt Cassel (QB) went to a Pro Bowl. He was a franchised player, however, and was acquired via trade.
Bart Scott (LB) has been a starter for the Jets
Jason Brown (C) has started 2 years for the Rams
Matt Birk (C) has started 2 years for the Ravens
Brian Dawkins (S) went to a Pro Bowl for the Broncos.
Antonio Smith (DE) had 8.5 sacks for the Texans.
Keith Brooking (LB) started two years for the Cowboys
Michael Boley (LB) started two years for the Giants
Jabari Greer (CB) started two years for the Saints.
That's 2 Pro Bowl players and 8 decent starters. That doesn't include major busts like T.J. Houshmanzada or Albert Haynesworth who started, but failed to play well.
There was much less player movement in 2010 due to the extension of restricted free agency to 6 years and the addition of an extra tag per team. There were 10 marquee free agents who changed teams, and 8 of them had value.
Karlos Dansby (LB) started 13 games for the Dolphins
Terrell Owens (WR) had 983 yards for the Bengals (I know, he's a stretch).
Neil Rackers (K) kicked for the Texans
Thomas Jones (RB) was basically terrible for the Chiefs, but had 896 yards rushing.
Dunta Robinson (CB) started for the Falcons.
Aaron Kampman (DE) had 4 sacks in 8 games for the Jaguars before getting hurt (another major stretch, but the Jags seemed happy with him).
Alan Faneca (G) started 16 games for the Cardinals.
That's one Pro Bowl player and basically a bunch of mediocre starters.
Since 2007, the top 84 free agents to change teams have produced (generously) 33 players worth having. Of those, only 12 made Pro Bowls, and only 5 made All Pro teams. Of the 12 who made Pro Bowls, 4 of those had to be acquired via trade and cost their new teams significant draft picks. By position, the valuable players were:
QB: 2 (Schaub, Cassel were both traded for)
WR: 3 (Welker, Curtis and Owens. Curtis and Owens count as 'worth signing' by the LOOSEST definition of the words)
RB: 2 (Turner, Jones)
OG/C: 7 (there were no tackles worth signing)
Interior linemen are hard to value correctly, so it makes sense that teams would miss value them (like Jake Scott). Guards are the easiest thing to find via free agency, as are situational pass rushing ends. Free agent widouts are a mess and should be avoided at all costs. The only truly quality wideout to change teams via free agency was Welker, and he had to be traded for.
As you can see, the list of 'impact free agents' is not a pretty one. Teams that invest big money in free agents are usually getting older players who simply don't merit big time pay. Aside from the offensive line, there's not much point in paying to get players another team has already decided it doesn't want.