Early career A right winger, during his final year with the Toronto Young Nationals in 1970–71, Middleton appeared in 42 games, scoring 39 goals and 34 assists. Following his stint with the Nationals, Middleton played two seasons with the
Oshawa Generals. During his first year with the club, Middleton appeared in 53 games and scored 70 points (36 goals and 34 assists). Later in the year, during a game vs. the
California Golden Seals, Middleton scored a career-best four goals as the Rangers won 10–0. During his rookie year, Middleton suffered multiple injuries that restricted him to 47 games; during that time, he scored 22 goals and 18 assists for 40 points. That year, he played in all three postseason games as the Rangers were eliminated 2–1 by the
New York Islanders. The following year, in 1975–76, Middleton appeared in 77 games for the Rangers and recorded 24 goals and 26 assists. The Rangers missed the playoffs that year. The transaction became even more one-sided in favor of the Bruins when head coach
Don Cherry developed Middleton's defensive skills, making him a solid two-way player. Hodge played only one more season before his career ended, while Middleton became a star in Boston. Middleton made his debut for the Bruins on October 7, 1976, versus the
Minnesota North Stars and scored a hat trick in a 6–2 Bruins victory. Middleton went on to appear in 72 games for the Bruins that year and scored 22 goals and 20 assists. The following year, during the
1977–78 season, Middleton had one of his best single-game performances vs. the
Cleveland Barons on March 21, 1978, when he scored two goals and three assists in a 5–3 Bruins win. He went on to appear in 79 regular-season games for the Bruins and scored 25 goals and 35 assists for 60 total points. The
1978–79 season saw Middleton have his first 30-plus-goal season as his numbers improved. In 79 games, he became a point-per-game player, scoring 38 goals and 48 assists. The following year, during the 1979–80 season, Middleton played in all 80 games for the first time in his career. He was once again a point-per-game player throughout the season, scoring both 40 goals and 50-plus assists for the first time, finishing the regular season with 92 total points. Middleton appeared in 10 postseason games, scoring 4 goals and 2 assists, as the Bruins were defeated by the New York Islanders 4–1 in the quarterfinals. During the offseason, Middleton signed a five-year contract extension with the Bruins. The
1980–81 season saw the Bruins hire former goalie and Middleton’s teammate Gerry Cheevers as their new head coach. Cheevers started playing Middleton on the power play, penalty kill, and first line, with Middleton now playing 20–30 minutes per game. Starting in the
1981 season, Middleton became one of the premier wingers in the league when rookie
Barry Pederson was placed on his line at center. He and Pederson clicked immediately and had three of the best seasons together of any two linemates in NHL history. Together, from 1981–84, they posted over 200 points per season. One of Middleton’s best seasons came in 1981–82, during which he played in 75 games and scored a career-high 51 goals and 43 assists for 94 total points. Middleton also won the
Lady Byng Trophy for excellence and sportsmanship, finishing the year with just 12 penalty minutes. In addition, he finished seventh in league scoring, placed first among all NHL players in shooting percentage with a 25.2%, and was named to the NHL's Second All-Star Team. The Bruins defeated the Buffalo Sabres in the first round, 3–1, but were defeated by Quebec, 4–3, in the quarterfinals. Middleton scored 6 goals and 9 assists in 11 playoff appearances. The following season in
1982-83, Middleton appeared in all 80 regular season games and scored 96 points (49 goals, 47 assists), The Bruins were then eliminated in the semifinals 4-2 by the Islanders. Middleton’s best statistical season came the following year during the
1983–84 season when appeared in all 80 games for the fourth time and scored 105 points (47 goals 58 assists) in which he tied Ken Hodge's team record for most points scored in a season by a right winger, and remains unbroken. and was named to his third and final NHL All-Star game. During the postseason he and the Bruins were swept 3-0 in the first round by the Canadians. The following year in 1983-84 Middleton would appear in all 80 games for a fifth in final time. His numbers would start to decline however he still managed to nearly be a point per game player finishing with 76 points season with 30 goals and 46 assists. His leadership was apparent in being named
co-captain (with
Ray Bourque) to succeed
Terry O'Reilly in
1985-86, a position he held until he retired, wearing the "C" during home games and Bourque would wear it at away games. During that season Middleton struggled to stay healthy as injuries in his shoulder early in the season, he then missed the end of the year with a concussion suffered after being hit in head with puck during practice on February 7, 1986. He retired with 448 goals and 540 assists for 988 points in 1,005 games, and added 100 points in 114 playoff games. Middleton made a brief comeback, playing one season in Switzerland in 1988–89 for EHC Bülach, scoring 11 goals and 14 assists in 25 games; however, he officially retired from the sport at the end of the season. Middleton scored 25 shorthanded goals for Boston—a Bruins' team record that was surpassed by
Brad Marchand in 2018–19. Middleton had held the club record for more than 30 years since overtaking
Derek Sanderson's record of 24. During his career, he recorded four 20-goal seasons, three 30-goal seasons, four 40-goal seasons, and one 50-goal season. Middleton is one of just seven Bruins to record 100 playoff points. Middleton was regarded as one of the best one-on-one players of all time and currently ranks second all-time in career shooting percentage (19.7) among players with 400+ goals. On November 29, 2018, the
Boston Bruins retired Middleton's #16 before a game against the
New York Islanders at
TD Garden.
International play Middleton also starred in international play and made his debut for
Team Canada in the
1981 Canada Cup. He appeared in seven games during the tournament, scoring 1 goal and 2 assists, as Team Canada was defeated by the
Soviet Union, 8–1, in the final. Middleton made his second and final stint with Team Canada in the
1984 Canada Cup, where he teamed on the top line with
Wayne Gretzky and
Michel Goulet. He recorded 4 goals and 4 assists in seven games, and Team Canada went on to defeat Sweden in the final to win the gold medal. == Coaching career ==