In October he was coaching the NHL's Florida Panthers. But after being fired in November, he was named the Canadian women's team coach and guided the squad to a stirring fourth straight Olympic title in Sochi, Russia.
Dineen is now with a third team, preparing the Canadian under-18 men's squad to defend its world title in Finland.
"It's been (a whirlwind) but you know what, it's a hockey life," Dineen said. "You have tough times with the lows, you get fired and it's an emotional deal.
"As I told the women before the gold medal game, I knew the day I was hired I had to be on my toes and it was kind of like someone lit a match under my fanny. I just really enjoyed that whole process. You never know how those things are going to end.
"Just like this one, you don't know. We've got to have some luck and have some things work in our favour but it's not always about the ending. It's about the ride you're on, it really is."
The 50-year-old Quebec City native will have plenty of international experience at his disposal when Canada begins its title defence Thursday against Sweden in Imatra, Finland. Thirteen players on the roster participated in last year's under-17 World Hockey Challenge in Quebec while eight skated in this year's under-17 event in Cape Breton, N.S.
And nine players helped Canada win gold at the Ivan Hlinka tournament last summer. However, Dineen's biggest challenge is quickly moulding his players into a tightly knit team.
"Yes there are challenges like having to gel and find some chemistry in a timely manner," he said. "A lot of the European teams have been together for a while and the Americans are centralized all year so those teams have an advantage.
"But that's what makes it fun putting this team together. These boys are really excited to represent Canada and that works in our favour. They're sharp kids."
And big, with 14 players being six feet or taller. But it's still a team, Dineen says, that can excel on the larger international ice surface.
"Even though I talk about our size, that does not in any way take away from our skill," Dineen said. "I think we're a team that has some skill and I believe we can compete with any team.
"That makes it enjoyable to have those guys who can play the game anyway we need to play to have success."
Dineen is familiar with international hockey. He played for Canada six times, claiming world championship silver medals in '85 and '89 and winning the '87 Canada Cup. The 19-year NHL veteran also wore the Maple Leaf at the '84 Winter Games.
In December, he joined a national women's program stinging from coach Dan Church's sudden resignation and having lost four straight pre-Olympic tuneups to the archrival United States. In Russia, Canada beat the Americans twice, including a thrilling 3-2 overtime decision in the gold medal game after trailing 2-0 late in regulation.
"If you were going to ride a roller-coaster and go the top, I couldn't have done better than that," Dineen said. "I had a pretty good buzz for about three weeks after Sochi, just enjoying it and the enjoyment people got out of that tournament.
"That's a special moment for Canada and you can compound that a lot for me and the players as well."
Since Sochi, Dineen has been overwhelmed by people anxious to share their Olympic experience. That includes former NHL goalie Fred Brathwaite, now an assistant coach on the under-18 squad.
"He was telling me he was on Highway 401 driving to a game and couldn't watch but found it on the radio," Dineen said. "After we scored in overtime, there was like 50 people around him all honking their horns.
"A fireman from Hamilton told me how they were so mad they had to leave on a call during the game and when they returned there was skiing on TV. They thought they'd missed it but it was just the holdover until overtime. The next thing you know, the whole firehouse was watching and went bonkers.
"When you hear those stories — and I've heard literally hundreds and will never tire of anybody's story — it's pretty special. I'm not afraid to share those experiences with these boys."
Moose Jaw Warriors forward Brayden Point, a late cut from last year's team, said Dineen has quickly made an impression on his young players.
"He's an awesome guy," said the 18-year-old Calgary native. " He's got real good systems and he's really good with the players.
"Everyone respects him a ton and it's real easy to learn from him."
Kingston Frontenacs defenceman Roland McKeown, a returnee from last year's squad, said Dineen's message is a simple one.
"He's preaching the Canadian way," McKeown said. "At the Olympics you saw how dominant the men's and women's teams were and that was doing it the Canadian way with hard work, that two-way game and everyone buying into a role.
"That's what we're going to do."
The six-foot-one 195-pound McKeown, an 18-year-old native of Listowel, Ont., hopes last year's experience helps him become a key contributor this time.
"Last year proved every guy has to take a role and buy in to win a championship," he said. "I gained a lot of experience from the guys who were here last year and want to use that to take a leadership role with this team."
Dineen has taken an unplanned detour to land behind the under-18 team's bench, but he's a better coach because of it.
"I coached six years in the American Hockey League and always took pride in being able to work with either veterans or young players but these guys are all young," Dineen said. "That really makes it enjoyable because they're a good bunch.
"To me, that's one of the advantages, just coming here and working with these players. You're getting better every day and that's a good thing for me."