[4] He also won a silver medal as a member of the Canadian national men's hockey team at the 1960 Winter Olympics[5] in Squaw Valley, California.

But in his second year, aided by the acquisitions of Phil Esposito, Ken Hodge and Fred Stanfield in a blockbuster deal with the Chicago Black Hawks, the team posted a winning record.

In October 1970, he published a story in Sports Illustrated declaring he had left the Bruins because of their mid-season refusal to give him a raise for the following year.

After a slow start, he led the Canadians to a come-from-behind win capped by Paul Henderson's series-winning goal with 34 seconds remaining in the final game.

Within days after the Summit Series, he signed a five-year deal to return to the Bruins as their general manager,[3] succeeding Milt Schmidt, who was named to the post of executive director.

Sinden, who had added the title of club president in December 1988, remained as the chief executive of the Bruins until the summer of 2006 when he retired to a consulting role.

Notwithstanding this longstanding success, he was the subject of controversies ranging from video replays to salary arbitration and was under frequent fire from Bruin fans.

In the 1996–97 season, the NHL fined him $5,000 USD for verbal abuse of a video-replay official[8] who had disallowed a goal in the second period of a game between the Bruins and the Ottawa Senators.

He is also a "Hockey GM & Scouting" instructor[10] for the online sports-career training school[11] Sports Management Worldwide, founded and run by Dr. Lynn Lashbrook.