"It's exciting for us," O'Reilly said Thursday night. "We know we can beat this team and do some damage here."
"We know that they have a lot of talent over there and they work hard, but for us, it's an exciting challenge," the Blues star added. "We're going have some fun and we're going to beat them."
The Avalanche clinched the Presidents' Trophy to claim the NHL's best record with a 5-1 win over the Los Angeles Kings on Thursday.
Colorado scored the most goals per game and surrendered the third-fewest per contest in 2021 while authoring the NHL's second-best goal differential. The Avalanche also led the league in goals for percentage at five-on-five and expected goals for percentage in the same situations, according to Natural Stat Trick.
O'Reilly, who played his first six seasons with Colorado, led the Blues with 24 goals and ranked second with 30 assists while playing all 56 games this season. St. Louis named him captain in December following Alex Pietrangelo's departure in October.
The Avalanche finished atop the West Division with a 39-13-4 record, while the Blues finished fourth at 27-20-9.
Colorado won five of the eight meetings between the clubs during the regular season, though St. Louis won the last two, both on home ice.
Game 1 of their first-round series is scheduled for Monday night in Denver.