The Buffalo Bills have been one of the unluckiest franchises in the NFL, losing four consecutive Super Bowls from 1990-1993. Similar to most teams in the league, the Bills have also had their fair share of failures in free agency.

Of course, Buffalo has made some fantastic signings in free agency, including the likes of London Fletcher and Mario Williams. But that still doesn't explain some of the decisions they've made over the years that have caused fans to scratch their heads in befuddlement.

While it's nice to look back at all of the successes that Buffalo has had in free agency, it's only fair that we point out the shortcomings they've had as well. In light of that, here are the five worst free agents signings that the Bills have made in their 61 years of existence.

5. Percy Harvin

Percy Harvin began his career with the Minnesota Vikings as a first-round pick in the 2009 NFL Draft. During his four seasons with the Vikings, Harvin became a valuable offensive weapon, recording 3,985 scrimmage yards and 24 touchdowns.

In addition, he also contributed five more touchdowns as a lethal return specialist. However, Harvin would deal with nagging migraines during his career and would proceed to spend short stints with the Seattle Seahawks and New York Jets after his tenure in Minnesota.

Despite his ineffectiveness in Seattle and New York, the Bills signed Harvin to a one-year, $6 million contract in 2015. Even though he spent two years in Buffalo, he combined for only 21 receptions, 224 yards and one touchdown in that span.

4. Vontae Davis

There aren't many players who have retired in the NFL following a game, let alone at halftime. But that is exactly what Vontae Davis did when he played for the Bills in 2018.

Prior to the 2018 season, Davis signed a one-year, $5 million deal with Buffalo. The expectation for Davis was to become a solid No. 2 cornerback alongside the up-and-coming star in Tre'Davious White.

However, after missing Week 1 in his first season with the Bills, Davis would retire at halftime in his debut with the team in Week 2 versus the Los Angeles Chargers. It's safe to say that the signing of Davis didn't go as planned.

3. Dwan Edwards

In his first six seasons in the NFL, Dwan Edwards managed to start in only 23 games with the Baltimore Ravens. Altogether, in his six years in Baltimore, Edwards accounted for only two sacks and six tackles for loss.

Nevertheless, the Bills decided to give Edwards a four-year, $18 million deal in 2010. Edwards would only last in Buffalo for two of those years, amassing a mere 3.5 sacks and five tackles for loss.

Just a year after leaving the Bills 2011, Edwards would notch a career-high six sacks in 2012 with the Carolina Panthers. There's no doubt that Buffalo would have loved to get that type of production from him to at least justify signing him in the first place.

2. Langston Walker

Marv Levy is forever memorialized as the greatest head coach in Bills history, leading the team to four Super Bowls during his tenure from 1986-1997. On the other hand, he didn't last long as a general manager with the organization from 2006-2007.

One of the reasons why he fell short of succeeding in the front office was due to his questionable spending on the offensive line. In his second year as the team's general manager, Levy chose to hand out $25 million over five years to Langston Walker in hopes he could bolster the offensive line.

From 2002-2006, Walker was a solid offensive lineman for the Oakland Raiders (now located in Las Vegas), starting 50 games. Though he started in 32 consecutive games with the Bills from 2007-2008, Walker would be released in 2009.

1. Derrick Dockery

Besides Walker, the Bills and Levy made another head-scratching move in free agency. As a matter of fact, on the same day that they inked Walker to a five-year deal, Buffalo completed a deal with guard Derrick Dockery.

Dockery signed a seven-year, $49 million contract that also included a guaranteed signing bonus of $18 million. Altogether, Buffalo doled out a total of $28 million in combined signing bonuses for Walker and Dockery.

Before joining the Bills, Dockery spent four seasons with the Washington Redskins. Similar to Walker, Dockery would last only two seasons in Buffalo, being released by the team in 2009. The signings of Walker and Dockery were seen as firable offenses by the Bills as they let Levy go as general manager after 2007.