On Friday, the stands of Wells Fargo Arena were empty. There were no screaming fans doused in blue or crimson. Neither school band appeared behind the basket to play a familiar tune after a made shot. Only the sound of the basketball and the coaches’ whistles could be heard.

But on Friday, it was what could not be heard in the arena that perhaps stuck the most in John Calipari’s and Tom Crean’s head.

A friendship that originated more than 20 years ago when Crean was an assistant coach at Pittsburgh and Calipari a head coach at UMASS, has now come full circle — the two are set to square off in one of the most anticipated games this NCAA Tournament.

And before the ball is thrown in the air in Saturday’s Second Round matchup, they’ll be shaking hands with a person they have spent a meandering journey with. They will be turned into 40-minute enemies.

“I think we have a friendship that transcends basketball,” Crean said. “He is a very encouraging person to me, I think I understand him, and I hope I’m encouraging to him.”

A few years after the two first met, both departed with brighter futures in mind. Calipari was en route to the NBA and Crean joined future Hall-of-Famer Tom Izzo as an assistant coach, but it would not be long before the coach from Mount Pleasant, Michigan, and the coach from Sewickley, Pennsylvania, met again.

Calipari quickly found the NBA was not his area of expertise, but was lucky enough to find himself back on his feet in Memphis — a job that possessed more pizzazz than any school in the country.

Why?

Because the man he confidently calls his “close friend” accepted a head coaching job at Marquette one year prior — both Calipari and Crean were now coaching in Conference USA. The two participated in spirited competition on the court while enjoying a steady friendship off it.

“I’ve always respected his work habits, his basketball knowledge,” Calipari said. “I loved being around guys that like to talk basketball and X and O and do goofy stuff like that and salt shakers and moving stuff around, and he’s one of those kind of guys. He’s into basketball.

“We knew your team better be ready or you’re going to get beat,” Calipari said. “We stay in touch. We talk once every couple of weeks or so.”

While the bond between the two men began to grow, so did their success.

During their tenure in Conference USA, Crean and Calipari saw ample Coach of the Year awards come their way, the two recruited and coached high-profile NBA players like Dwayne Wade and Derrick Rose and both led their programs to a Final Four.

While one coach endured success, the other acted as a sponge, absorbing any and all knowledge he could carry over to his program.

“I learned a lot over the years from him as a coach,” Crean said. “We were in the league together, Conference USA, when he came back to Memphis. I learned a lot, not only coaching against his teams, but watching them play others.”

Next, the two stepped onto college basketball’s brightest spotlight — Crean took the reigns of an Indiana program that was on the decline and Calipari joined forces with UK after the Big Blue Nation had an unsatisfied two years with Billy Gillispie.

At that time, the Hoosiers and the Wildcats still had a home-and-home series, one that dated back to 1969. Calipari was the first to hit the road in the historical rivalry, and came away with a 90-73 victory at Assembly Hall in the first IU-UK/Crean-Calipari saga.

The Cats went on to take the next game in Rupp, but it was the 2011 game that most fans remember.

Calipari and his No. 1 ranked Cats came into a deafening Assembly Hall with an unblemished record and a team loaded with NBA talent, but it was the Hoosiers who stood tall as the buzzer sounded. Christian Watford’s buzzer-beater sent waves across the nation, and arguably sent Calipari away for good.

There has not been an IU-UK home series since. Crean was persistent in renewing the home-and-home series, but Calipari would not budge because he only wanted neutral site games.

The friendship remained unharmed despite its scheduling differences.

“We had our moments with that, but no, I think if you have a respect level for somebody you have to overlook some things,” Crean said. “I have a ton of respect for them.”

Now they’re here in Des Moines, Iowa. The stands will no longer be empty, the bands no longer quiet. The official will toss up the ball while cameras flash and two coaches who share decades of friendship will look down the sidelines and realize the setting.

They are 40-minute enemies.