Bill Callahan guided Nebraska to a 27-22 record in his four years in Lincoln from 2003-07. He led the Huskers to 9-5 mark in 2006 that included a Big 12 North Division title and a trip to the Big 12 Championship Game. Nebraska lost to Oklahoma, 21-7, in the conference title game at Arrowhead Stadium, before earning a New Year's Day bowl invitation to the Cotton Bowl. NU fell to Auburn, 17-14, to close the 2006 season.
After seeing steady improvement in his first three seasons, beginning with a 5-6 record in 2004 and advancing with an 8-4 mark and tie for second in the Big 12 North in 2005, the Huskers took a step back in Callahan's final season in 2007.
Nebraska finished with a 5-7 record - the Huskers' second losing season in four years under Callahan. The seven losses represented the most by an NU team since 1958.
While Nebraska's offense continued to score points in the West Coast offensive philosophy installed by Callahan, averaging a more than respectable 33.4 points per game, the Husker defense struggled by historic standards, surrendering 37.9 points per game.
Callahan was removed by Athletic Director Tom Osborne at the conclusion of the 2007 season, and former Nebraska defensive coordinator Bo Pelini, who had just helped LSU to a national title as the Tigers' defensive coordinator, was hand-picked by Osborne as Callahan's replacement.
Callahan was originally hired by then-Athletic Director Steve Pederson on Jan. 9, 2004, to replace Frank Solich. However, Pelini had spent one game as Nebraska's interim head coach, leading the Huskers to an Alamo Bowl victory over Michigan State before moving on to serve as the defensive coordinator at Oklahoma.
Callahan came to Nebraska less than a year removed from leading the Oakland Raiders to Super Bowl XXXVII after winning the AFC West title in 2002. He became the fourth rookie head coach to reach the Super Bowl. He led Oakland to an 11-5 regular-season record in his first year and went 4-12 in 2003, when the Raiders were hit hard by injuries.
In his first season at Nebraska, Callahan installed the West Coast Offense and the Huskers struggled to a 5-6 record, NU's first losing season since 1961. In 2004, with a year of learning the new system, Nebraska rebounded with an 8-4 record that included a 32-28 Alamo Bowl victory over No. 20 Michigan. NU finished the season with a No. 24 final national ranking in both major polls.
The Huskers continued to build momentum in 2006 by working their way to a 9-5 record that included a 6-2 regular-season Big 12 mark. NU defeated top-25 Missouri and Texas A&M teams late in the season before rolling to a 37-14 win over Colorado to claim the Big 12 North title. NU entered the 2006 Big 12 Championship Game ranked 19th nationally, but were tripped up by No. 8 Oklahoma, 21-7.
The No. 22 Huskers ended the season with a 17-14 loss to No. 10 Auburn in the Cotton Bowl, before going 5-7 in 2007, giving Callahan nine losses in his last 14 games on the sideline at Nebraska. NU did not end the season in the national rankings in either 2006 or 2007.