Kerr grew up in Tecumseh, a community near Windsor in southwestern Ontario. He played junior with the Windsor Spitfires and the Kingston Canadians of the OHA, where he was a decent scorer even if he wasn't prolific. Had he not grown so much as a teenager, he would have put up bigger numbers. As it was, he soldiered on as his coordination slowly caught up with his size.
With 230 pounds on his 6'3" frame, Kerr was known around the junior leagues as a slow skater who parked himself in the slot, collecting his share of "garbage" goals. He was never drafted by an NHL team but was signed by the Flyers after a 40-goal season in junior in 1979-80. He suited up immediately with their AHL affiliate in Portland, Maine, where he scored six points in seven games.
He played decently at Philadelphia's training camp in 1980 but didn't convince everyone that he could succeed in the NHL. In the end, he made the team because a broken leg suffered by Ken Linseman opened a spot on the roster. Kerr registered 22 and 21 goals in his first two seasons and established himself as an NHL regular. In 1982-83, he was on pace to top the 40-goal mark when a serious knee injury ruined his season.
Teamed with Brian Propp and Dave Poulin, Kerr took his game to another level in 1983-84. The tag "Sultan of Slot" became an apt description of his important role on the team. He recorded his first of four consecutive 50-goal seasons and became one of the most feared and closely checked forwards in the league. Regardless of how much physical abuse came his way, he stood his ground and used superior hand-eye coordination to pot goals almost at will. The NHL hadn't seen an individual dominate the slot since Phil Esposito was in his prime. More important, Kerr wasn't a streaky scorer. He never slumped and totaled over 50 goals for four years from 1983 to 1987.
The fortunes of the Flyers rose with Kerr's ascent to stardom. His presence on the ice could change the entire aspect of a game. Philadelphia reached the Stanley Cup finals in 1985 and won the first game against the favored Edmonton Oilers before succumbing in five games. Kerr notched 10 goals in 12 matches and drew accolades from his opponents. As usual, he attracted plenty of harsh attention from the Edmonton checkers, but Kerr was neither deterred nor drawn into taking penalties for retaliation.
During the 1985-86 season, he scored 58 goals, a personal high he equaled the following year. That first year he also set an NHL record with 34 power-play goals. This had an enormous impact on the strategy of opponents, who didn't dare get into penalty trouble against the Flyers' extra-man unit.
Philadelphia reached the finals against Edmonton for the second time in three years in 1987 and pushed the eventual victors to seven games before falling short. Unfortunately, Kerr suffered a shoulder injury that prevented him from playing in the finals. In addition to the individual sorrow it caused him, the team was heartbroken and felt he may have made a huge difference in such a close series. Following the season, Kerr was elected to the NHL Second All-Star Team.
A 48-goal season in 1988-89 was the last time Kerr made a huge impact in the NHL. His dedication was acknowledged when he was presented with the Bill Masterton Trophy that summer. The physical pounding by the opposition took its toll. Kerr played parts of two seasons with the New York Rangers and Hartford before retiring in January 1993. He immediately accepted an assistant coach position with Springfield of the AHL, the Whalers' top farm club.