"I was watching the game and the whole place where I was eating dinner was chanting Jagr's name," Seguin told reporters after Canada's practice on Friday.
"I started chanting too and I took a video of it. Jar-o-mir Jagr!"
Seguin won't be chanting Jagr's name on Saturday, when Canada meets the Czechs in a semifinal which is sure to draw a vocal partisan crowd to Prague's O2 Arena.
Already a national hero for his two Stanley Cups, two world championship gold medals and his gold with the Czech Olympic team at the 1998 Nagano Games, the 43-year-old Jagr announced his retirement from international competition after the Czechs finished fourth at the 2014 world championship.
He reversed his decision after a strong finish to the 2014-15 NHL season, when he had 18 points in 20 games after a trade-deadline move to the Florida Panthers.
Canada defenceman Aaron Ekblad had just turned two years old when Jagr and the Czechs ousted Canada in a shootout in the Nagano semifinals.
Ekblad admitted that he was "a little starstruck at first," when Jagr arrived in Florida in March, "but seeing how nice of a guy he is, how patient he is and how good of a teacher he is with all the young guys including myself in Florida, he's definitely an asset for any team."
"He's a strong guy," added Seguin, who played with Jagr on the Boston Bruins during the late stages of the 2012-13 NHL season. "Not only on their power play but a lot of their plays, their system goes through Jagr or (Philadelphia forward Jakub) Voracek. We've got to know where they are on the ice and make sure we key on them."
Canada held Jagr to a single assist during a 6-3 win over the Czechs in the preliminary round.
"That was a pretty tough game," Ekblad said. "I'm expecting something similar to that.
"I'm not talking the outcome — I'm talking how hard they work. They're a great team and they had a lot of opportunities to score against us so we're going to try to limit that."
Though Canada leads the tournament with an average of 7.25 goals scored per game, head coach Todd McLellan says his group continues to emphasize defence.
"We've been fortunate that way, that when we get ourselves in trouble we can score our way out of it," said McLellan. "But I think as the competition narrows starting tomorrow, that's going to be a lot harder to do.
"We can't just think we're going to score our way to wins. We've got to check our way to wins."
And of course the crowd noise at the O2 Arena will be dialled up for the semifinal. Edmonton Oilers forward Jordan Eberle said he is looking forward to the game experience.
"When the crowd's going and they're whistling and they're jumping and all that — we enjoy playing in front of it too," Eberle said. "Even walking around the square — people love hockey. They're passionate about it, much like Canada. When you get a matchup like this, it's going to be a lot of fun."
The Czechs may have the crowd support, but Canada remains the team to beat with a perfect record through the first eight games of the tournament.
When asked if that creates added pressure on his team, McLellan said: "When you are from Canada and you put the jersey on, it comes with the territory.
"Yeah, there's pressure. But there's a lot of those players that have played either in this type of event, Olympics, Stanley Cup finals - you name it, they've been involved with it. The pressure exists the minute you accept the responsibility of putting the jersey on. It's nothing that anybody hasn't dealt with."