The 18-year-old homegrown is closer than ever to joining Chelsea, who spent a reported $15 million with add-ons ($10 million base) for the goalkeeper in what amounts to one of the largest-ever fees paid for an MLS youth product.
Slonina, who will report to his new club in January 2023, is already envisioning what awaits him on the other side of the pond under new manager Graham Potter.
"I'm super excited just to be in that environment and see what it's like in the Premier League," he told co-hosts Susannah Collins and Jillian Sakovits during The Call Up's latest episode.
"How the coach acts when we win, when we lose, what's the locker room look like? Just that level of pressure, I can't wait to be in there and be in that environment because I think you're going to learn from every single person there."
Slonina has handled his rise well, becoming the youngest-ever goalkeeper to start an MLS game (17 years, 81 days) last season and quickly establishing himself as Chicago's undisputed No. 1. He's posted 16 clean sheets across 43 games for the Fire, and just this week was named No. 4 on the 2022 edition of 22 Under 22 presented by BODYARMOR.
These performances didn't go unnoticed, and Chelsea wasted little time in securing his signature ahead of clubs like Real Madrid.
"The path that they showed me and presented me while I was talking to them was something I really liked," said Slonina, who committed his international future to the United States instead of Poland despite a recruiting push from his parents' homeland.
"They really focused on a player's development and making sure they're seeing the right things, playing games and getting minutes. Because obviously for a young goalkeeper, that's super important. You can train a lot, but you still have to see those game minutes and everything. I was drawn to the fans, to the location of where it's at. And it's Chelsea, so it was a no-brainer.
Slonina may be loaned out at Chelsea, with Senegal international Édouard Mendy and Spain international Kepa Arrizabalaga the Premier League side’s top two options. He joins the Blues on a six-year contract through 2028.
Before heading overseas, Slonina experienced a dip in form this summer. That prompted a call from another US goalkeeper in the Premier League, hearing from Arsenal’s Matt Turner.
“He just told me that even when he was young, he made a lot of mistakes,” Slonina said of the former New England Revolution standout. “And I'm going to make mistakes young in my career and they're going to be highlighted because a lot of the times, it's sad to say, but a lot of people look for mistakes to have something to talk about. He just told me to keep going and trusting in the path, keep working every single day and you'll find that form again. He was a big help.”
The Chicago native is poised to become Chelsea teammates with Christian Pulisic, too, having met the USMNT's captain this past winter in a camp for World Cup qualifiers.
"I did give him a message when I was in Chelsea, signing and everything," Slonina said. "He said he's super excited for me to be with the club and hopefully we can see the field together."
For more from Slonina, check out his full interview here.