Who remembers back in the mid-1990s when the Nebraska football team was one of the greatest teams in college football history?
The Cornhuskers made three-straight national championship appearances from 1993-95, winning the last two of those titles. The Cornhuskers also won the championship in 1997, capping off the 25-year career of legendary coach Tom Osborne.
The offense that Osborne ran was an option-style offense. Quarterback Tommie Frazier and running backs Lawrence Phillips and Ahman Green were focal points of the power-running offense during Osborne's tenure, and those championship teams either led the entire nation or were close to the top in rushing, scoring offense and total offense.
Osborne retired after the 1997 season, and his assistant Frank Solich took over as head coach. The Cornhuskers never made it back to the title game under Solich, and they went 10-3 overall and 5-3 in the Big 12 Conference in his last season as the coach in 2003.
Then came the beginning of the Callahan era.
He had previously coached the National Football League's Oakland Raiders to the Super Bowl in 2002. Two years later he parted ways with the Raiders, and brought his west-coast style offense to Nebraska. The team struggled to adapt to the new scheme, going 5-6, 3-5 in his first season at the helm.
The players he had at the time were used to running the option-based offense, but his teams have progressively gotten better as he has been able to recruit the players that fit his system.
Last year the Huskers went 8-4, 4-4, and defeated the Michigan Wolverines 32-28 in the Alamo Bowl. This year his team sits at 5-1, 2-0 going into Saturday's matchup with K-State at Snyder Family Stadium, and Callahan has his system going strong.
"We've got players that are capable of playing a lot of different roles," Callahan said about the guys he has been recruiting since he arrived at Nebraska. "It does give you a certain amount of flexibility and the system can adapt to a lot of variables."
The catalyst to the Cornhusker offense is quarterback Zac Taylor.
The west-coast offense is predicated on a quarterback who can stay in the pocket and throw high-percentage passes, and that is exactly the kind of player Taylor is.
"This is a very capable quarterback," K-State coach Ron Prince said. Prince is doing exactly what Callahan did three years ago. He is in his first year implementing a west-coast offense into a team that has been known as an option-based program, so he knows how vital the quarterback position is.
"He's as dangerous as we're going to find. I think they go into each game and decide how they're going to play that game and how it needs to played. They're very functional in that they can play a different style of game every week."
Taylor has completed 95-of-143 of his passes for 1,398 yards, and has 13 touchdowns to just two interceptions. His passer efficiency rating of 175.8 is second in the country.
Because of the emphasis of throwing the ball with the new system, Taylor has been able to break numerous records during his one and a half years with the Huskers.
He is the single-season record holder for passing yards (2,653), completions (233) and attempts (399). He is also Nebraska's single-game record holder for passing yards (431), completions (36) and attempts (55).
His total of 4,051 career yards ranks him fourth on Nebraska's all-time list, just ahead of Frazier.
This season Callahan's offense is third in passing offense in the Big 12 (253.2 yards per game), fourth in the nation in scoring (39.7 points per game) and seventh-best in the country in total offense (463.8).
"You can just tell from watching their games and watching their film that they're more comfortable running their offense this year than last year," Wildcat linebacker Zach Diles said. "Everybody has been in the system for a couple of years now so they're definitely more comfortable running it."