When he retired at the end of the 1982-83 season, Cashman was the last survivor of the Original Six. Cashman played junior in Oshawa with Bobby Orr, but he was a winger with not much speed or skill. But, he was the best in the league in the corners, and it was his superb work that got the puck to centre Phil Esposito in the slot time and again so that Espo could break all goal-scoring records (their linemate was Ken Hodge, part Cash, part Espo).
His first game came in 1964-65 as an emergency recall when the Bruins were short of forwards. Two years later he earned a full-time job in Beantown, and he became known as a scrapper and player both. He played on the historic Summit Series Team Canada team in 1972, but his career was jeopardized in 1972-73 when he slid into a goal post and hurt his back. Undaunted, he continued to play. In fact, it was easier for him to skate than either walk or sleep. But by seasons end he could barely move.
After a serious operation, he recovered, and in 1977 was made the Bruins captain. He returned to play aggressively and maintain his ability to score 20 goals a season, though the team's playoff runs were always both consistent and not particularly lengthy. Six years later, he retired.
In 1986, Esposito, now GM on Broadway, hired Cashman as a scout for New England, the start of a prominent post-skating career in the game. After five years with the Rangers, he acted as an assistant coach for Tampa Bay for four years and moved to San Jose for 1996-97 in the same capacity. On July 7, 1997 he was named coach of the Philadelphia Flyers, and a week later as an assistant for Canada's entry in the 1998 Olympics. However, partway through his first year, GM Bobby Clarke removed him from behind the bench but kept him on as an assistant and advisor. After four seasons with the Philadelphia organization, Cashman became head coach of the ECHL Pensacola Ice Pilots before returning to the team he spent his entire NHL playing career with the Boston Bruins, as an assistant coach in 2001-02.
Winner of two Stanley Cups, Cashman played (17 years, 1,027 games) with the Boston and is still one of the most loved Bruins of the modern era.