Nicknamed "The Riverton Rifle" and "The Chief", Leach was drafted third overall by the Boston Bruins in the 1970 NHL Amateur Draft. Boston traded Leach, Rick Smith and Bob Stewart to California for Carol Vadnais and Don O'Donoghue on February 23, 1972. After playing three seasons in Oakland, the Golden Seals traded Leach to Philadelphia for Larry Wright, Al MacAdam and 1974 first rounder (Ron Chipperfield) on May 24, 1974. He contributed to the Philadelphia Flyers' Stanley Cup win in 1974-75. He finished his NHL career with a one-season stop with the Detroit Red Wings.