Rest easy, New York City FC fans. Ronny Deila knows a promise is a promise.

Back when he was hired, Deila vowed to The Third Rail supporters group that he would celebrate shirtless if he could lead NYCFC to MLS Cup.

Now that he's one game away, co-hosts Susannah Collins and Jillian Sakovits did the only responsible thing when he appeared on The Call Up, checking to see if the manager would stick to his word Saturday at Providence Park if they beat the Portland Timbers (3 pm ET | ABC, UniMás in US; TSN, TVA Sports in Canada).

"I think I have to do that," he said. "It’s tough. I’m not 35 anymore. I’m 46 now, so it’s going to be harder, and I don’t think my kids are going to be very proud of me. But it’s worth it, it’s very worth it."

Deila has developed a habit of this throughout his managerial career: He previously performed a similar celebration when helping Norwegian side Strømsgodset avoid relegation from the country's top flight over a decade ago. He has also attended the occasional team meeting au naturale.

And there's an underlying meaning to his promise to don his underwear for us all. Or at least that's what he told The Call Up crew.

"In these moments, you have to be a little bit crazy," Deila said. "To play confident, you have to be crazy. You have to go out and show yourself and not be scared to do mistakes. And this is a little bit some symbol of that: go out, express yourself, show who you are. And if you do that, you have a good chance to win."

Check out Susannah and Jillian's full interview with the NYCFC boss below.