A frustrating reality in the life of an NFL general manager is that sometimes one of the players you gloss over, cut, trade or just let walk away in free agency will succeed for another NFL team. Below are 10 particularly vexing examples -- nine players and one head coach -- of such oversights from the past 25 years. Several of these examples will mention Football Outsiders' advanced stats such as DVOA and adjusted sack rate, which are explained here.
10. Tramon Williams, CB, Houston Texans
Undrafted coming out of Louisiana Tech in 2006, Williams was signed by the Texans and had eight tackles and a pass breakup during the 2006 preseason before he was waived in early September. The Green Bay Packers added Williams to their practice squad two months later and signed him to a "reserve/futures" contract when the season ended. Playing a minor role as an extra defensive back and occasional starter from 2007-09, Williams was productive and totaled 129 tackles, including a quarterback sack, with 10 interceptions and 33 passes defensed. Inserted as the full-time starter opposite Charles Woodson in 2010, Williams had a breakout season, intercepting a career-high six passes and earning his first trip to the Pro Bowl. He also signed a four-year, $33 million contract extension before adding three more interceptions during the Packers' run toward a fourth Lombardi trophy.