Colaiacovo, who became an unrestricted free agent this summer, was not brought back by the Blues and signed a two-year, $5-million contract with the archrival Detroit Red Wings.
Colaiacovo, 29, arrived at the arena Saturday morning and had to remind himself where he needed to be.
"Actually, I got locked out when I came in," Colaiacovo quipped. "I didn't know where to go. I'm still used to being a home player here. I didn't know where the visiting teams were supposed to go.
"I've seen a lot of familiar faces and it brings back a lot of good memories. I obviously still have a lot of great friends on that team. I saw them last night and saw them again this morning. A lot of mixed emotions going through me today. The adrenaline's going to be rushing through me tonight. I know that the crowd's going to be rocking. It's a new opportunity for me, a fresh start. I'm looking forward to making the most of it."
Blues defenseman Alex Pietrangelo is one of Colaiacovo's best friends. The two were paired together for much of last season in St. Louis and spent Friday night together catching up over dinner.
"When you're on the ice, you're competitors," said Colaiacovo, who has recovered from a shoulder injury suffered while playing in the Spengler Cup. "That's what you grow to be, that's what you are at the end of the day. Everything on the ice is through competitive nature. You do things hard but you be respectful when you do them."
"You're an opponent. As close as we are, it is what it is," Pietrangelo said. "You've got to go out there and play the game. I've got a lot of friends on a lot of teams. It's part of the game. You laugh about it after the game.
"It almost feels like a guy that hasn't left yet, but at the same time, I know he's focused on what he's got to do over there. It's going to be a fun one tonight. He's turned the page. It's a new chapter in his career. He's excited to be there."