Jim O’Neil is walking a tightrope.

Northwestern’s new defensive coordinator is replacing a legend in the retired Mike Hankwitz, a beloved figure whom O’Neil’s boss, head coach Pat Fitzgerald, liked to call “the G.O.A.T.”

Yet, at the same time, O’Neil has to make the defense his. He said at the beginning of spring practice in early March that while he wouldn’t fix what wasn’t broken, he would add new wrinkles to Hankwitz’s highly successful system.

Yet one thing is clear in spring practice: the unit that O’Neil is inheriting isn’t the same one that finished fifth in the nation in scoring defense in 2020. He’s lost four critical pieces in the back seven that formed the foundation of one of the best defenses in the nation.

At linebacker, O’Neil lost two-thirds of the Irish law firm of Fisher, Bergin & Gallagher. Gone are Paddy Fisher and Blake Gallagher, and their combined 736 tackles, 47 tackles for loss, nine interceptions and 12 forced fumbles over the last four years.

Then, in the secondary, he lost half of the starting quartet that anchored the No. 1 pass efficiency defense in the country. Former Wildcat cornerback Greg Newsome could hear his name called in the first round of next Thursday’s NFL draft, and J.R. Pace was a three-year starter who picked off eight passes in his career.

But O’Neil isn’t too worried about filling those player’s extra-wide shoes. He is excited about the guys waiting to step into them.

While Chris Bergin is the lone holdover still racking up billable hours at linebacker, O’Neil mentioned three new names who could form their own law firm in the near future. And one of them has a very familiar name.

“Obviously we know about Bergin, he’s played a lot of football,” said O’Neil after Saturday’s final spring practice. “But a couple young guys that I thought had really taken a step in the right direction is KJ (Khalid Jones), Cullen Coleman (and) Bryce Gallagher -- the new Gallagher has stepped up.”

Jones is a redshirt junior who has patiently waited three years for an opportunity to start. Coleman, who is still in his first year in Evanston, chose Northwestern over offers from Alabama, Ohio State and Notre Dame, among others. Gallagher, a redshirt sophomore, is the younger brother of Blake, who started the last three years at linebacker.

"I think those guys that graduated did such a great job leading that room and help developing those guys and Timmy McGarigle is an unbelievable linebackers coach, so don’t be shocked if those guys still play at a high level,” said O'Neil.

Among the defensive backs, O’Neil singled out three Cats who caught his eye.

“I am really intrigued by Garnett Hollis (Jr.) coming off of surgery. He did some great things at the tail end of spring, he’s a corner,” said O’Neil. “I thought Rod Heard had an unbelievable spring practice. I thought Jaheem Joseph is a freshman that came in, we moved him to safety and he did some great things.”

Hollis is a long, 6-foot-1 corner who did not appear in a game this fall, while Heard made one start and appeared in nine games as a corner. Joseph arrived in Evanston as a corner but now will be a second Joseph at safety, joining freshman All-America Brandon (no relation).

"I thought a lot of guys this spring put themselves in a position to earn a role for themselves come training camp when real jobs are made," he said.

And O'Neil made it clear that everyone's job is up for grabs with a new coach in place.

"I told the guys: there are guys that played a lot last year, (but) in the game of football you have to earn it every year," he said. "Just because you were an All-American or just because you were a starter last year, that doesn’t mean anything. You gotta earn it every single day at practice, you gotta earn it every game, that’s the way it is."

In addition to adjusting to his new personnel, O’Neil has had to adjust to the college game. It’s been 13 years since he last coached college football. When he left his job as safeties coach at Eastern Michigan in 2008 to take his first job in the NFL, George W. Bush was in the White House and the Big Ten had just 11 teams.

Yet, according to O’Neil, not that much is different from the NFL to the college game. The practices, in terms of length and tempo, are largely the same. And offenses still use formation variations and attack personnel, the same as they do in the NFL, he said.

The biggest differences, according to O’Neil, is that colleges run the quarterback much more and have different formation rules. For example, in college, offenses don’t have to have an eligible receiver on the back side of the formation, like they do in the NFL, so a team can line up four wide receivers on one side and none on the other.

But, so far at least, O’Neil seems to be enjoying his new role teaching college kids instead of pros.

“As far as just being a Northwestern Wildcat, it’s been awesome,” he said. “The players have exceeded my expectations. I told them that today. I tried to break them down mentally with all the install that we threw at them and they didn’t let me do it.

“And then I’ve just been blown away by the culture that (Coach) Fitz and these players have built here. It’s just been better than expected. A lot of people at every level and in every sport talk about culture but it’s not real, and it’s real here and it’s been fun to be a part of the last couple months.”