Minutes after their Sweet 16 victory over Iowa State on a Thursday night that turned into an early Friday morning, Illinois’ players were ready to celebrate. Inside their locker room in the bowels of TD Garden, they just needed one man – their coach, Brad Underwood – to step inside to get the party started. They anticipated his entrance, with mini water guns in hand.

But they weren’t expecting this: Suddenly, the 60-year-old Underwood broke through the black curtain to the locker room without a shirt on. He had goggles on, and he was spraying his team with an even bigger water gun. The party was on.

“I don’t know if I thought I’d see the shirt off with the water gun,” forward Marcus Domask said.

The stocky Underwood gives off a serious demeanor, but he knows when to have fun. He said it’s important. The program’s first Elite Eight berth certainly qualified, even if it produced a sight for sore eyes.

“I don’t want winning to ever, ever just be a relief,” Underwood said. “Like whew, next game. I don’t want that. I want them to enjoy that moment. For whatever it is, 30 minutes, whatever it is. … This makes you never want to quit coaching. It’s not the winning. It’s who they are. Every one of these guys is a comedian in their own right. Yet, we know when to flip the switch.

“Yeah, they’ve got a 60-year-old man taking his shirt off and doing his best dad bod. So probably not very good, not very easy to look at.”

The Fighting Illini are loose, and there’s no sense of anxiety. “We are jittery,” Underwood said sarcastically on Friday. If you didn’t know any better, you wouldn’t have a clue they were preparing for the biggest game of their lives, a meeting with No. 1 juggernaut UConn on Saturday night at TD Garden with a spot in the Final Four on the line.

The Huskies, fresh off a 30-point victory over San Diego State, look unbeatable in their quest to become the first repeat national champion in 17 years. They’re not only winning, they’re blowing the doors off opponents. The Illini aren’t worried about it, and hearing them talk about 24 hours before the huge matchup, they’re almost brushing off this seemingly Herculean task.

“I feel like there’s, like, no pressure on us,” Illinois senior Coleman Hawkins said. “I feel like it’s another game.”

The Illini weren’t completely familiar with their opponent. Domask said he has only watched the exciting tournament games, which eliminated his desire to watch UConn’s blowouts. After their locker room party, the preparation began early Friday morning. UConn, the nation’s No. 1 offense per KenPom, runs some of the most unique and complex sets in the sport.

But, at least publicly, Underwood wasn’t overwhelmed.

“It’s not overly complicated,” Underwood said. “They are who they are, we are who we are. …

“They run a lot of sets, nothing that we haven’t seen throughout the course of Big Ten play and postseason.”

This matchup features the No. 1 and No. 2 offenses in the country, but the outcome might come down to physicality. UConn coach Dan Hurley said it’s going to be a “bloody battle” between two of the best rebounding teams in the country. The Huskies secured 21 offensive rebounds in Thursday’s win over the Aztecs, and that’s been a point of emphasis from Underwood.

While UConn has made bludgeoning its opponents look routine, Hurley doesn’t anticipate a trip back to the Final Four to be easy. Not against these Illini, who have won seven consecutive games.

“One of the best teams in the country,” Hurley said. “We expect a 40-minute war going into every game that we go into.”

There’s a certain level of comfort for a UConn team that was on this stage and broke through last season. Hurley admitted it was “pretty nerve racking” then. But now, they look at ease.

“Feels different,” Hurley said. “We broke through last year. We’ve established a level. Maybe we feel a little less pressure as an organization because we feel like we’ve established a level now of where our program’s at, that we’re going to be in this spot moving forward. Obviously, this year and moving forward.

“I don’t think we feel the same anxiety. We have tremendous respect for our opponent, know how hard tomorrow is going to be. But we’ve established a level that we expect to be back to.”

“I know they’re hungry to break through and get to a Final Four,” Hurley continued. “We’re hungry to get back to a Final Four. We’re two of the truly best teams in the country.”

Given its dominance, it would be a shock if UConn lost on Saturday. No one has proven to even test the Huskies. But there’s a quiet confidence about Illinois, with its water gun celebrations, that suggests it’s not worried about any of this. They’re playing with house money, and a certain stubbornness that could be beneficial. While some may be overwhelmed by this stage, this moment is not too big for them.

“Age, old, maturity,” Underwood said. “I mean, Marcus is a 2,000-point scorer. Quincy’s (Guerrier) played in 160 games. There’s nothing that they haven’t seen. There’s just some value in that. It’s not like you’re running a bunch of young guys who don’t know what they’re going to do. I know what this group’s going to do. I know how they’re going to react.”