Therrien was Bouillon's coach in junior hockey when they won the Memorial Cup with the Granby Predateurs and was coaching him again when the stocky Montreal Canadiens defenceman celebrated his 38th birthday on Thursday.
"Time goes fast," said Therrien. "But when you look at success stories, here's a guy who was never drafted, he played in the ECHL, he played as a 20-year-old in the Quebec league when we won the Memorial Cup together.
"He's had such a great career."
Bouillon, the Canadiens' oldest player, beat the odds by making it to the NHL as a five-foot-eight defenceman and beat them again by carving out a long career.
His playing days looked to be finished when Montreal cut him (and his $1.8 million salary) loose in 2009, but he went to the Nashville Predators camp on a try-out and made the team. Then he played well enough for the Preds to offer him a two-year extension.
He looked to be headed for retirement again in 2012, but then the Canadiens hired Therrien back as head coach and Bouillon got a one-year contract. Now he's on another one-year US$1.5 million deal.
"Today, it's important to have good contacts," said Bouillon. "When Michel got hired last year and I got the call from him to sign here, I was really happy about that.
"Today, you need to have good relationships with people. I had it with Michel in the past, and to have a chance to play for him again is a pleasure."
His job this season is partly to play and partly to be the on-ice mentor to gifted rookies Jarred Tinordi and Nathan Beaulieu.
The Canadiens have three injured veterans on the back end — Alexei Emelin, Douglas Murray and Davis Drewiske — so the youngsters have been taking turns in the lineup, mostly on the third pairing with Bouillon.
"As a defenceman, it's always nice to have one partner for the whole season, but for me, it's been maybe three years, since I was in Nashville, that I played with a few different guys," he said. "Here I play with Tinordi or Beaulieu. They're both playing really good. They're young but they play with a lot of confidence."
The job entails playing on the right side, which has been an adjustment for the left-shooting Bouillon.
"The hardest part has got to be your vision when you get a puck," he said. "On the strong side, I know what's coming on the other side. Playing on the right is a bit different, but now I've played a few games there and it's getting better."
Bouillon has never been a flashy player. His best season was 2005-06 when he had three goals and 19 assists. But he moves the puck well, plays on the second power play unit and is very strong for his size. He doesn't fight much, but he doesn't shy away from physical play either.
Defenceman Josh Gorges said the Canadiens lost a warrior when they let Bouillon get away, and he was glad to see him return.
"When I first came here (in 2006), he was one of the guys I really looked up to and who really helped me get settled in," said Gorges. "People counted him out early in his career, in the middle of his career and late in his career, and he's still there playing at a high level.
"That's a testament to his work ethic and his demeanour as a person."
After going undrafted, Bouillon played a season for the Wheeling Nailers in the ECHL before moving up to the AHL with the Quebec Citadelles after Montreal signed him as a free agent in 1997. Two seasons later, he was in the NHL.
He was born in New York City and moved to Montreal when he was three, but retains his U.S. citizenship. He even played for the Americans at the 2003 IIHF world championship.
Whether Bouillon is back next season is to be determined. When Emelin returns, likely in late November or early December, and when Murray is healed in a few weeks, spots in the starting lineup may be scarce.
And the rookies he is working with may soon be ready for full-time NHL action.
"I take it year by year," he said. "I don't want to think long-term. If I'm healthy and I've still got a passion to play hockey, I'll be there again next year.
"For me, being 38 doesn't matter. I feel pretty good."