It's ironic, in a way, because O'Reilly learned how to be a hockey pro in Denver, playing his first six NHL seasons with the Avalanche. Colorado traded O'Reilly to the Buffalo Sabres in 2015, and Buffalo traded him to St. Louis three years later.
In 2018-19, his first season with the Blues, he won the Selke Trophy, awarded to the best defensive forward in the NHL, and helped St. Louis win the Cup.
"[Denver] is where my NHL career started," O'Reilly said at the start of the series. "It was very important to me and I had a great time. It's always nice to see people appreciate it, but the focus goes back to hockey."
The focus always is on hockey for O'Reilly. That is what has helped him evolve into an elite two-way player and emerge as one of the game's most effective leaders.
Avalanche forward Nathan MacKinnon saw the start of that evolution, playing with O'Reilly for two seasons (2013-15).
Since then, MacKinnon has watched from afar as O'Reilly's game and legacy have grown exponentially. They likely will see a lot of each other during the series, just as they did last season, when the Avalanche swept the Blues in the first round.
Though MacKinnon got the upper hand in that series, he knows he will have his work cut out for him this time. They went head-to-head in Game 1, and Berube and Avalanche coach Jared Bednar each seems comfortable with that matchup.
"[O'Reilly] is just good everywhere, so it's going to be a hard matchup for sure," MacKinnon said. "I just think positionally there's no cheating in his game. He's not going to sacrifice defense to try to get points or whatever. He's got a really good stick, he's a really good face-off guy. Just a smart player, really tough to play against."
O'Reilly, in his second season as Blues captain, has emerged as a security blanket, the player to be counted on when things need to be settled down or when momentum needs to be changed. Each is a necessity in Game 2.
The Blues are confident the best version of O'Reilly will show up, because it usually does in these situations.
"I mean, it always looks better when you produce [on the score sheet], but I don't think it matters if he produces or not," Perron said. "He just plays the right way all the time."