Leach was drafted in the fifth round by the Phoenix Coyotes. After spending several years in minor hockey leagues, he signed as a free agent with the National Hockey League's Boston Bruins on September 26, 2003. While with the Bruins he appeared in his first two NHL games during the 2005–06 season, collecting no points and seven penalty minutes. Leach spent most of his time in the Bruins organization with their AHL affiliate in Providence. On July 3, 2007, he was signed as a free agent by the Tampa Bay Lightning. He played in two games for the Lightning during the 2007–08 season but spent most of the season in the AHL. On February 26, 2008 he was traded to the Anaheim Ducks. Later, during the summer of 2008 he signed with the New Jersey Devils. On November 6, 2009, Leach was claimed by the Montreal Canadiens on re-entry waivers from the Devils. On November 28, 2009, due to a high number of injuries to Canadiens forwards, Leach played forward instead of his usual defense position. Leach was claimed off waivers by the San Jose Sharks on December 1, 2009, and he played 28 games for the Sharks during the season. He recorded his first NHL goal in an 8 to 5 victory over the visitingNashville Predators on March 11, 2010. He began the 2010–11 season playing for the AHL's Worcester Sharks, but on February 9, 2011, he was traded back to the New Jersey Devils along with Steven Zalewski in exchange for Patrick Davis and Mike Swift.
Coaching career
Leach became an assistant coach with Adler Mannheim of the Deutsche Eishockey Liga in 2014, helping the team in winning their sixth DEL Championship. On July 7, 2015, Leach was appointed as assistant coach to Mike Sullivan for the Wilkes-Barre/Scranton Penguins, affiliate of the Pittsburgh Penguins of the NHL. Leach was named interim head coach in December 2015 after Sullivan was promoted to be the head coach at Pittsburgh before settling into the position of associate head coach on a permanent basis to new Wilkes-Barre/Scranton head coach Clark Donatelli. Leach departed the Penguins after one season, eventually joining the Providence Bruins as an assistant coach on August 4, 2016. He would be promoted the P-Bruins head coach position prior to the 2017–18 season.
