You can take the man out of Slavia Prague, but you can never take the Slavia Prague out of the man.
That's not how the expression goes, but it's something like that.
And when the Czech side eventually got the better of the Foxes to make the last 16 of the Europa League, he was the first person they called to join in the celebrations from afar.
Soucek is something of a legend in Prague, where he scored 40 goals in 158 appearances over three-and-a-half years before leaving for a club record £15m last year. It seems his ex-teammates - who came up with one of the shocks of the round as they eliminated Brendan Rodgers' side on their own patch - haven't forgotten his contributions.
Throughout the night, Soucek had been making his support clear with a succession of Instagram stories showing him at home wearing a Slavia shirt. He then posted a message at full-time, captioning a picture of the Slavia players celebrating which read: "Congratulations! Great honour SKS!"
Slavia's Twitter account even acknowledged his contributions to the win in their slew of post-match tweets, which continued throughout the night and spilled over into the morning. Someone's enjoying themselves.
The win itself was an ultimately close-fought encounter. After a 0-0 draw in Prague, an away goal was always likely to prove crucial, and the Czech side got theirs when Lukas Provod slammed in at the back post following some abject Leicester defending.
Slavia's win was then virtually ensured with ten minutes to go when Abdallah Sima fired past Kasper Schmeichel.
Slavia will find out their opponents later on Friday, and the Czech league leaders could face Manchester United, Arsenal, Tottenham or Rangers. They are a regular fixture in the knockout stages of the Europa League and made the semi-finals back in 1996 - a feat they will be dreaming of repeating, or even bettering, now their name is in the hat.