When Kirby Smart hired Mel Tucker to be his defensive coordinator three years ago, it was never about  if he would leave someday for a head coaching job, it was when.

The move came this week after Tucker accepted the job as coach at Colorado in the Pac-12. He’s going to start immediately, which means he won’t run Georgia’s defense in the Sugar Bowl against Texas.

He has been exceptional during his three years at Georgia, and he’s going to be missed. He was beloved by his players, especially the guys in the secondary whom he spent the most time with. He was a great recruiter and worked very well with Smart in setting the tone for this perennial top-15 defense.

All that is gone now. And it will be tough to fill all of those shoes.

“When I came to Georgia in December of 2015, one of my top priorities was to bring Mel Tucker in as defensive coordinator,” Smart said. “He is an exceptional coach, coordinator and trusted friend. I think change is kind of inevitable, you know that that’s going to happen in this profession, (and) you know that coaches get opportunities. When you’re a part of a successful program and you’re able to win games, you’ll have guys get opportunities.”

That’s always how it works in college football. Struggling teams look to successful programs for their next head coach. Colorado was no different, looking for someone to get them over the hump. They’ve been better the past few years, and they want Tucker to make them conference title contenders.

He can do that.

Tucker is certainly ready to be a head coach. He has spent nine years as a defensive coordinator in the NFL and was even the interim head coach of the Jacksonville Jaguars for five games. He has been an assistant on two national championship teams — at Ohio State (2002) and Alabama (2015) — and has worked with some of the best coaches in the business, like Nick Saban, Jim Tressel, Mark Dantonio and, of course, Smart.

Tucker also coached defensive backs at Georgia aside from being the coordinator. He has turned Deandre Baker into one of the best cornerbacks in the country, and Baker appreciates it.

“Coach Tucker, he’s a great guy, a great coach,” Baker said. “He played a big role in the Georgia program. He’s going to go over there to Colorado and change the program around. I’m happy he got an opportunity to be a head coach.

“He groomed me into the player I am today. He taught me the ropes, and I took it and ran with it.”

Tucker has always been a well-respected recruiter as well. He was rated the No. 14 recruiter in the country by 247Sports.com last year, and he has been in the top 20 in their recruiting rankings all three years at Georgia.

It’s going to be interesting to see who replaces Tucker, and this is going to be Smart’s most important personnel move since assembling his staff in the first place. Inside linebackers coach Glenn Schumann is an option because he has been with Smart the longest and is considered a rising star at only 29 years old. There would be plenty of external candidates with ties to Smart as well, so it’s going to be interesting to see how this plays out.

Tucker and Smart worked well together. The biggest misconception the past three years has been that Tucker was just a stand-in for the defensive-minded Smart and that Smart was really running the defense. That’s not true, though Smart certainly had impact over the course of the week of preparation, and on game day.

This was Tucker’s deal, and he ran with it. We knew this day was coming, and it’s too bad it’s here. But, when you’re an elite program, it happens and you move on.

The next move, though, is going to be interesting.