But the former Oakland Raider head coach says his current roster of players has been receptive to change.
"When we began spring football I told the players that the installation was going to be of a high volume and exceptionally aggressive," said Callahan, who was fired after two seasons as an NFL head coach. "I really felt that at the conclusion of spring the players were very receptive of what was going on. The volume of plays that were asserted was the same as I had at the pro level. The reception that we had made for a great spring.
"I feel totally confident in what we're implementing and have accomplished so far. Our players have been open, resilient, and been in the position to allow this new system and staff to implement it. These guys have been born and bred in Nebraska tradition and have put their spirit on the line in what they do from a preparation standpoint. These are the guys that will make this system go and change happen."
Two positions that will be particularly important for Nebraska to have success in Callahan's first year are quarterback and offensive line. Returning backup quarterback Joe Dailey is the likely candidate to take lead the offense, but Callahan has yet to name him the starter for Western Illinois.
As a true freshman, Dailey played a limited role for the Cornhuskers, passing for 117 yards and two scores on 9-of-14 completions. His main competition figures to be junior Mike Stuntz, a Council Bluffs, Iowa, native.
"We'd like to establish a quarterback to take over the reigns," Callahan said. "The quarterback is the most important player and part of our offense. I've never been a rotation guy and a coach that's had two quarterbacks playing at one time. We'd like to go into the season with a starting quarterback and work from that point on.
"I think we've got great competition. Whether it's Joe Dailey, Mike Stuntz, Zach Miller or Garth Glissman, we want somebody to emerge at the conclusion of training camp that knows the system and executes well. Joe Dailey has exhibited the ability to take the edge and become the starter. But it's still wide open heading into training camp."
The biggest adjustment has been done on the offensive line, where players have been asked to switch from a run-blocking mindset to a system that will likely pass more than rush. Callahan said his line has made the adjustment quickly, and gives some of the credit to former position coach and current Iowa State assistant Barney Cotton.
"So much has been said about the West Coast offense and this offensive system, but the offensive line has to make a positive transition," Callahan said. "The success of our offense will be predicated on the offensive line. We've got players that have been very versatile. We have retooled and restructured every aspect of our offensive line. Guys have made a number of position moves."
"Prior to that transition they have had some previous experience from Barney Cotton, so it's already occurred in some aspects. But the terminology is different and it varies somewhat. This is a tough skill to learn. It's a master skill and takes time and patience. For the most part I think our guys have adapted well."
‘Happy to be in Lincoln'
Callahan was the center of a well-publicized feud with some players at his former stop in Oakland. Rumors had him losing control of his team. Players said they had lost respect for Callahan as coach. When the dust settled from the Raider debacle, Callahan all of a sudden found himself out of a job just one year after making the Super Bowl in his first season as head coach.
The new Nebraska head coach spoke briefly on the 2003 season, but preferred to focus on his return to college football.
"A lot of things got misrepresented in my previous experience and it doesn't do any good to rehash that," Callahan said. "You learn from every experience that you go through. I wasn't completely satisfied with how the operation was run and voiced my opinions. Things didn't work out the way we wanted them to, but I don't want to diminish or take away from where we're at right now. I'm proud to be a Husker and look forward to all of the things ahead."