"I was just asking a girl on a date," the Oakland Raiders sixth-string tight end said before practice on Tuesday. "And it turned into something much bigger."
To be fair, that "girl" has been on the international gymnastics stage for years now, and when three-time Olympic gold medalist -- and ESPN The Body Issue participant -- Aly Raisman accepts a professional football player's advances, people talk.
Especially on social media.
In fact, it was in a video where Underwood made his inquiry, and on a responding video where Raisman accepted.
Those videos, though, have been playing on a loop in the Raiders' locker room, much to Underwood's chagrin. Even if his colleagues are paying him respect.
"I was like, 'Hey man, you put yourself out on a limb there, bro,'" quarterback Derek Carr said with a laugh.
"That's a lonely feeling being out there on a limb, man. I'm happy for him, and she made a good decision saying yes, because he's a really good guy. He really is. Besides all the football stuff, he's a really good person, so I hope it works out for him."
Coach Jack Del Rio agreed.
"We have a celebrity in our midst," he said. "It's amazing how things get traction. I think young men doing what young men do, and [he] invited out a really decorated Olympian, so that's a pretty neat story.
"When you put yourself out there, you want to get that yes back, so congrats for him."
This was not some blind-date, shot-in-the-dark situation. In fact, it was semi-set up by backup long-snapper Andrew East, who is married to another former U.S. Olympic gymnast in Shawn Johnson.
And while Underwood and Raisman have exchanged pleasantries over FaceTime, they have not spoken since she agreed to the double-date with East and Johnson.
"She did a great job and her whole team did of representing the USA [in Rio de Janeiro]," Underwood said. "So I felt like it was only right for me to send a congratulations and extend an offer when she got back to the U.S. and had some down time.
"Now I'm going to have to figure out a time in the schedule with the season coming up, but she's actually scheduled to be out here in September, so I'm looking forward to attending that show and catching up with her."