Ex-UConn coach Bob Diaco in his element as Nebraska DC

(AP) One moment, Bob Diaco is congratulating one of his charges for a job well done with a fist-bump and slap on the back.

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The next, he is charging at a linebacker who slipped out of position on a drill. Chin to facemask, and loud enough to draw the attention of sideline observers, Diaco asks him why he messed up. Apparently satisfied with the answer, he taps the linebacker on the shoulder pads and moves on.

That's the thing about Nebraska's new defensive coordinator. He's always moving. There's no time to waste. Diaco is installing his 3-4 defense, a massive undertaking this spring in a program that has used the four down linemen-three linebacker base alignment since the early 1990s under five head coaches and seven coordinators.

Diaco's system produced excellent results at Notre Dame, where he was coordinator from 2010-13. His work with the Fighting Irish earned him his first head coaching job at Connecticut. Abysmal offense was his undoing at UConn, and in December he was fired. Nebraska coach Mike Riley swooped in to hire the 44-year-old Diaco as the replacement for Mark Banker.

The native of Cedar Grove, New Jersey, had just interviewed for the Arkansas defensive coordinator's job in January when Riley asked him to come to Lincoln for a visit. Diaco accepted an offer of $825,000 this year and $875,000 in 2018, making him the highest-paid assistant in Nebraska history.

As a coordinator, Diaco said, he's back in his element.

"If there was any liability or issue with being a head coach," he said, "it was being pulled away from the thing that you love the most, which is teaching and building an intimate relationship with either the unit or a position, because that bond is so special and fun to cultivate and grow."

Diaco's enthusiasm was on full display the first day of spring practice. Someone fumbled, and Diaco went to the ground to recover it himself.

"He's animated. He's hands on," linebacker Chris Weber said. "He makes it very clear what he expects."

Diaco is surrounded by mostly young assistants and an old hand in safeties coach Bob Elliott. Diaco and the 63-year-old Elliott worked together at Notre Dame in 2012-13.

"Coach Diaco is strong in his beliefs," Elliott said. "This defense and his ideas on football and life in general are very strong and principled. As a great communicator he can lay down those principles and sketch out how we're going to operate in a very precise manner. Bob Diaco could go 100 different places and have things up and running in a heartbeat."

The Huskers ranked 30th in the nation in total defense last season, a significant jump from the previous year, but they were vulnerable to the big play. That, and the Huskers' poor tackling, cost Banker his job.

Diaco's defenses at Notre Dame allowed just 14 plays of 50 yards or longer in 3,551 snaps over four years. Banker's defenses surrendered 12 of those plays in 1,740 snaps the last two years.

Seven starters return on defense, including four in the secondary. Diaco's biggest challenge is the front seven, where a number of players are learning new positions in the 3-4. Mick Stoltenberg, for example, has moved from being one of two tackles in the old 4-3 to nose tackle. Carlos Davis, previously a tackle, is now an end. Dedrick Young has moved from outside to inside linebacker.

The learning curve is steep, but the teacher's passion is undeniable, and the hope is that it rubs off on the players.

"It's not instantaneous," Diaco said. "You have to build a relationship. You can be an excitable, demonstrative coach if you're not using disrespectful words and demoralizing words and emasculating words and dehumanizing words. They want to be coached. You build a relationship and communicate with respect and love. Being nice and telling people what they want to hear is not my version of love."