It was a cardboard cutout of Iowa coach Fran McCaffery, whose team has become a more intense rival of Illinois through two heated matchups this season. The Illini got the better of the Hawkeyes in a 78-76 victory Sunday -- and the last laugh on social media after Underwood's signature on McCaffery's face.
"I didn't know what I was actually signing," Underwood said on the Laurence Holmes Show on Monday afternoon. "Then I looked down, I said, 'Hey, that's Fran.' So, I just continued on with it. I'm not on social media, but my daughters informed me it got a little action anyway.
"Rivalries are great. And I have so much respect for Fran. I love their team, I love their kids. For those 40 minutes or however long it takes to play, guys are going to compete and play really, really hard. I think it's great for college sports and great for college basketball in particular.
"I respect them. They play their tail off, and so do we."
The Fighting Illini improved to 21-10 with the win and earned the No. 4 seed in the Big Ten Tournament, which gives it a double-bye into the quarterfinals. Illinois will open conference tournament play Friday -- possibly against Iowa, which is the No. 5 seed and will play its opener Friday.
Illinois is a lock to make the NCAA Tournament, regardless of the outcome in the Big Ten Tournament. And Underwood is confident in the run his Illini can make in what's a wide-open field this season.
"I've been doing this 33 years, and I don't remember a year with so much parity," Underwood said. "We usually have five to eight teams, maybe, that have separated themselves and are a little bit better. This year is not that case.
"Michigan was a No. 5 seed in the (2018 Big Ten) tournament and goes to the Final Four. When you play in the Big Ten and you make postseason play, you got a chance to do something great. Matchups are always a big part of it. You got to catch a break here or there, as Virginia did last year.
"We can be as formidable of an opponent as there is out there."