Broncos likely to switch to 4-3

The Denver Broncos just officially announced the hiring of New Orleans secondary coach Dennis Allen as their defensive coordinator.

Denver also hired linebackers coach Richard Smith and linebacker coach Ron Milus. Both Smith and Milus were with John Fox in Carolina. Fox has now brought five of his Carolina coaches with him to Denver. The pair both coached in Denver under Mike Shanahan and Smith was a defensive coordinator in the NFL.

Allen, 38, is beginning his first stint as an NFL defensive coordinator. He is considered one of the bright young defensive minds in the league and in addition to Smith, Allen can also rely on Fox –- a defensive specialist -- as he grows into his new job. The Broncos hope Allen will bring stability to a unit that has had six different coordinators in six seasons. They were last in the NFL in 2010 in total defense and points allowed under coordinator Don Martindale.

Fox has previously said he was open to running either a 4-3 or a 3-4 defensive front scheme. Fox ran a 4-3 in Carolina and Allen has been coaching a 4-3. Denver has used a 3-4 defense for the past two seasons and team will likely add a lot of players on the defensive line and linebacker, so a switch to the 4-3 would matter much.

The key to the switch will be finding to effectively use Elvis Dumervil. Shanahan drafted Dumervil and the fifth-year linebacker flourished in a 3-4 defense in 2009. Dumervil, who was given a huge contract last summer, led the NFL with 17 sacks in 2009 but missed the entire 2010 season with a pectoral injury. He will probably be moved back to a rush end spot in the 4-3.

With Allen being hired, there are now two key coaching openings remaining in the AFC West. Kansas City needs an offensive coordinator and Oakland needs a defensive coordinator.