The frustration of not making the playoffs has altered the defensive coaching staff of the Denver Broncos.

Despite finishing a respectable sixth in yards allowed in the NFL, Broncos defensive coordinator Ray Rhodes has submitted his resignation and assistant head coach George Dyer, considered one of the better defensive line coaches in football, is leaving to join the Detroit Lions as their defensive line coach.

"Ray Rhodes has resigned as defensive coordinator because he felt like he wasn't getting the job done," the Broncos said in a statement.

However, two league sources and a team source said late Saturday that Rhodes, the former head coach of the Eagles and Packers, would have been dismissed had he not tendered his resignation. His relationship with head coach Mike Shanahan had deteriorated, particularly after a Nov. 11 loss to Oakland, one in which Rhodes was criticized for not making adjustments.

Rhodes started the season with one of the strongest defenses in football. He moved Pro Bowler Trevor Pryce from tackle to end and built one of the best defensive lines in football. A poor finish, however, left the Broncos frustrated and out of the playoffs at 9-7.

Under Rhodes, the Broncos allowed 301.6 yards a game, but 208.6 of those yards were allowed through the air. As the Broncos went into the final month of the season, defensive tackles Chester McGlockton and Lional Dalton and cornerback Deltha O'Neal found themselves getting less playing time.

Keith Millard is currently on the staff to work with the defensive line, but Shanahan will have to begin the search for a defensive coordinator.

Rhodes met Friday with Shanahan, who excused him from his contract, The Denver Post reported Saturday, citing unnamed Broncos and NFL sources. NFL sources believe Rhodes will be the primary candidate to join Mike Holmgren in Seattle as the Seahawks defensive coordinator, the Post said.

Holmgren recently fired five assistants, including defensive coordinator Steve Sidwell.

Denver's problems started with its 34-10 loss to Oakland, when the Raiders used short passes to find holes in the Broncos' soft coverages.

The Broncos rushed only two players at times and dropped their safeties into a deep zone, allowing the Raiders to chip away underneath. Oakland's Rich Gannon completed 34-of-38 passes, including a record 21 straight, providing a blueprint on how to attack the Broncos.

Opponents used the tactic effectively over the next few weeks, leading to close losses to Indianapolis, San Diego and the New York Jets. The Broncos lost five of their last seven games to miss the playoffs after a 6-2 start.

Rhodes was the NFL coach of the year with Philadelphia in 1995 and became the first coach to lead the Eagles to the playoffs his first two seasons. He spent four seasons with the Eagles before being fired in 1998, then spent one season as Green Bay's head coach before being fired.

Rhodes has a 38-44-1 record in five seasons as a head coach.

Rhodes played seven seasons as a defensive back and wide receiver for San Francisco and the New York Giants in the 1970s. He started his coaching career in 1981 as a secondary coach with San Francisco, and was an assistant with Shanahan when the 49ers won the Super Bowl in 1994.

Rhodes spent one season as Washington's defensive coordinator before joining the Broncos in 2001.

Information from ESPN.com's John Clayton, ESPN.com's Len Pasquarelli and The Associated Press was used in this report.