The Oakland Raiders are diligently working to find their head coach for the 2015 NFL season. While the team continues to consider hiring interim head coach Tony Sparano on a full-time basis, owner Mark Davis is exploring multiple options, having interviewed five candidates.

Mike Shanahan might be the most surprising coach to have interviewed with the Raiders. He had a poor relationship with the organization after coaching the team in the late 1980’s, but it appears the two sides are at least discussing the possibility of a reconciliation. Shanahan didn’t have much success with the Washington Redskins from 2010-2013, suffering three losing seasons and failing to win a playoff game. But the head coach won two Super Bowls with the Denver Broncos, and there’s a possibility he and his son, Kyle Shanahan, could try to help turn around Oakland.

The Raiders have reportedly met with three other former head coaches, one of whom is currently an assistant on a team in the postseason. Denver Broncos offensive coordinator Jack Del Rio, having been the head coach of the Jacksonville Jaguars from 2003-2011, is a leading candidate. Oakland is also considering San Francisco 49ers tight ends coach Eric Mangini, who coached the New York Jets for three years and the Cleveland Browns for two more seasons. Philadelphia Eagles offensive coordinator Pat Shurmur, who replaced Mangini in Cleveland and won just nine games in two years, interviewed for the job, as well.

A few offensive coordinators who have never been head coaches have interviewed for the job. Pep Hamilton has been the offensive coordinator for the Indianapolis Colts for two seasons, and he’s being considered by the Raiders. Darrell Bevell might not be able to accept a head coaching job for a few weeks, considering he’s an assistant coach with the Seattle Seahawks, but he also has a chance to replace Sparano.

Oakland hasn’t been linked to any of the recently fired head coaches that could be back on the sidelines next season. After being let go by the Jets, Rex Ryan has interviewed with the Atlanta Falcons, and is reportedly being pursued by the Buffalo Bills. Doug Marrone opted out of his contract with the Bills, and he’s been tabbed by some as the favorite to be hired by New York.

Mike Holmgren has reportedly told Oakland that he’s not interested in being their head coach. The former Super Bowl winning head coach has said he’d only return to the sidelines with the 49ers, but San Francisco is not interested in the 66-year-old as Jim Harbaugh’s replacement.

Since they reached the Super Bowl in the 2002 season, seven different permanent head coaches have led the team and failed to record even one winning record. Dennis Allen was fired after losing the first four games in 2014 and going 8-28 overall. Sparano went 3-9 in the final 12 games, winning three of Oakland’s final six contests.