Ruel died at his home in Longueuil, Que., on Monday at age 76 after spending his entire hockey career in the Canadiens organization, mostly in scouting and player development.
He had hoped to be an athlete, and as a teenager was a promising hockey defenceman and baseball player who had been invited to the Cleveland Indians camp. But he lost sight in his left eye while playing for the junior Hull-Ottawa Junior Canadiens in a pre-season game in Belleville, Ont., in September, 1957.
"I wanted to take a shot but the defenceman Ross Kowalchuk got his stick up a little high in front of me," Ruel later said of the incident. "His stick got me in the eye and not only did it leave me one-eyed, it ended my career as a hockey and baseball player."
With Ruel injured, Hull-Ottawa coach Sam Pollock moved winger J.C. Tremblay to the defence. Tremblay went on to become one of the best puck-moving rearguards in the NHL and later in the World Hockey Association.
His playing career gone, Ruel was named coach of the Junior Canadiens at 19 and became head scout of the NHL team a few years later.
Although he liked to work in the background, Ruel was thrust into the limelight twice as head coach of the Canadiens from 1968 to 1970 and again from 1979 to 1981.
He disliked the stress of being head coach and worked mostly as a scout, an assistant coach under Scotty Bowman of a team that won four straight Cups in the 1970s, and as director of player development until 1995.
One player he visited on a scouting trip in Rouyn-Noranda, Que., was Rejean Houle, who is now head of the Canadiens alumni association.
"I had the privilege to win Cups in the 1970s with Claude," said Houle. "When we needed help, he was always there for us.
"He helped a lot of players become what they are today."
Ruel was named head coach in 1968, replacing the legendary Toe Blake.
"I can't expect to do what Toe Blake did, he's the greatest coach ever, but somebody has to take the job and I feel confident," Ruel said.
In his first season, the Canadiens finished first overall with 103 points and won the Stanley Cup. But they missed the playoffs the next season and he was replaced by Al McNeil midway through the 1970-71 campaign.
He reluctantly agreed to replace Bernard (Boom Boom) Geoffrion early in the 1979 season, and stepped down in 1981 in favour of Bob Berry.
"We lost a great hockey mind and an incredible talent evaluator who contributed to the success of our hockey club for half a century," Canadiens president Geoff Molson said in a statement.
Players Ruel either drafted or helped develop included Hall of Famers Guy Lafleur, Yvon Cournoyer, Guy Lapointe, Serge Savard, Larry Robinson and Rod Langway.
Many credit Ruel with helping them develop their skills to become NHL players.
"Claude would come two weeks before camp and work us out on the ice," Robinson said in a recent interview. "A lot of it was movement, getting the puck, passing the puck, receiving the puck, shooting the puck.
"He had a way of creating mobility. Most of the guys on our defence could skate and could move around with the puck."
Ruel coached 305 NHL games and had a record of 172-82-51.
"I loved this man," former Canadiens forward Chris Nilan wrote on Twitter. "The single most important person in my development as a hockey player."
The Canadiens have also recently mourned the death of legendary captain Jean Beliveau on Dec. 2, forward Gilles Tremblay in November and defenceman Carol Vadnais in August.