The Montreal native used to rule the building, with sell-out hordes of 21,273 chanting his name after big saves, until he struggled last season and finally was dealt to Colorado at the March trade deadline for goaltender David Aebischer. Aebischer will be in goal for Montreal.
"It's obviously something special," Theodore told a mob of reporters Friday before the Avalanche practice. "I don't know what to expect.
"It's my first time back. It should be a great experience and a fun experience. I approach it like I want to play well and win, but it's not about proving that anyone made a mistake. It's just about me coming back and playing in my home town again."
He expects to hear a few boos "to try to get me off my concentration" and will try to focus on stopping the puck.
It helps that the Avalanche won the first two games on a three-game swing through Eastern Canada - 4-1 in Toronto and 2-1 in Ottawa - and that Theodore had what he called his best game this season against the Senators on Wednesday night.
Theodore struggled out of the gate this season, but now has a reasonable 2-2-1 record with a 2.81 goals-against average and .902 save percentage.
Coach Joel Quenneville said there was no question of keeping Theodore safe on the bench and starting back-up Peter Budaj.
"It was an easy decision," he said. "He's your No. 1 guy and you want him there in important games."
Theodore played himself out of the starting goaltender's job in Montreal with a weak post-lockout season in 2005-06, just after signing a US$16-million, three-year contract.
The strong play of French goalie Cristobal Huet made him expendable and general manager Bob Gainey was widely applauded when he unloaded Theodore's contract for Aebischer, who earns $1.9 million.
Aebischer went from the starting job in Colorado to a back-up role in Montreal, but has outplayed Huet so far this season.
"Because it's in Montreal, it will be a bit more special for Theo," said Aebischer, who added he bears no ill-will toward Colorado for trading him.
Another Av making his return to Montreal is Patrice Brisebois, a target of Bell Centre boo-birds for years for his high-risk approach to playing defence until he signed as a free agent with Colorado in 2005.
Brisebois may have made a tactical public relations first strike Friday morning when he turned up at Ste-Justine children's hospital to present a $50,000 donation for some new medical equipment. How can they boo a guy who does that?
Theodore's former teammates say the crowd should welcome back a player who had some very good seasons in Montreal - including a phenomenal 2001-02 when he won the Hart and Vezina trophies.
"He was the backbone of this team for a lot of years," said defenceman Craig Rivet. "Things didn't work out for him last year, but life goes on. He represented us well."
Theodore was at times the author of his own undoing for his off-ice adventures, which were mostly overlooked so long as he was playing well.
He was in the news when his father, an uncle and four half-brothers were charged in connection with a loan-sharking ring, although the goaltender was never implicated.
And last December, he tested positive for a banned substance that turned out to be an ingredient in a potion to prevent hair-loss. He was not suspended.
Only last summer, he was on front pages again for an alleged fling with celebrity Paris Hilton, although he said they only talked at a party.
Canadiens coach Guy Carbonneau empathized with Theodore. Carbonneau was all-but chased out of town during his time as Canadiens captain when, a day after they were eliminated from the playoffs, he showed the finger to a photographer while playing golf.
"I care about what a player does from 7 p.m. to 10 p.m. (during a game) and what he does outside of that doesn't matter," said Carbonneau. "I was paid to play hockey.
"If I want to have a beer or smoke a cigarette, that's my business. I don't think people should be able to go into that side of a player's life."
But they do, especially in Canada, where hockey rules all sports.
It is one aspect of playing for the Avalanche that Theodore appreciates - no one invades his private life.
"I really enjoyed playing here in Montreal - I had success here and it was great - but it's another lifestyle," he said. "Now I'm really enjoying Colorado.
"I went to watch Monday Night Football in Denver and I was able to walk around. I didn't have to sign any autographs. nobody noticed I was there. It was different."