After playing with the Toronto based Eaton's team, which won the Ontario Hockey Association championship in 1911, Foyston turned pro with the Toronto Blueshirts in the National Hockey Association in 1912. There he centered Hall of Famers Scotty Davidson and Jack Walker and the team won the Cup in 1914.
In 1915, Foyston and several Toronto teammates jumped to the newly minted Seattle Metropolitans of the Pacific Coast Hockey Association, where he was named best all-round player in that league. He scored an impressive 36 goals in 24 games and was named MVP. Foyston led Seattle in scoring 7 goals in 4 games to lead the Metropolitans as they became the first American based team to win Lord Stanley's Cup, defeating the Montreal Canadiens in 1917.
Foyston was conscripted into World War I service in 1918, serving with the Royal Flying Corps. He barely missed any of his hockey season though, returning to Seattle missing only two games.
The 1919 Stanley Cup was cancelled due to the Spanish Influenza and no winner was declared. This also cancelled one of the greatest individual performances ever in hockey history, as he scored 9 goals in the series prior to the cancellation.
The Mets returned to the Stanley Cup in 1920 as the PCHA champs, but dropped the series to Ottawa.
After nine seasons in Seattle, Foyston travelled north to join the Canadian Hockey League's Victoria Cougars, leading them to the Cup in 1925. The Cougars were the last non-NHL team to win the Cup. The Cougars were sold the next year and became the NHL's Detroit Cougars, forefathers of the Red Wings. Foyston went with the team but returned to the Pacific Northwest following his retirement from hockey.
Frank Foyston was not only one of the all time greats ever to perform with a hockey stick; he was also one of hockey's true pioneers. "The Flash" was inducted into the Hockey Hall of Fame in 1958 despite playing just 64 games (scoring just 17 goals) in the NHL, all late in his career.
Though he played most of his hockey out west and for a rival league, he was such a respected player. He was a true big game player - he scored 25 goals in 25 career Stanley Cup games, as well 174 regular season goals in 202 PCHA games and another 37 goals in 56 NHA games.