Shack played junior hockey for the Guelph Biltmores of the
OHA for five seasons starting at the age of 15. He had his best season in 1956–57, when he led the league in assists and starred in the
Memorial Cup playoffs. The
New York Rangers signed Shack and assigned him to their
AHL Providence Reds farm team for half a season. He made the
NHL in the
1958–59 season and played two years for the Blueshirts. In 1960, he was to be traded with
Bill Gadsby to the
Detroit Red Wings for
Red Kelly and
Billy McNeill, but the transaction was cancelled when Kelly decided to retire rather than accept the trade. In November of the
1960–61 season, Shack was traded to the
Toronto Maple Leafs, where he played seven seasons on the left wing as a colourful, third-line agitator who was popular with the fans despite a lack of scoring prowess. Canadian sports writer Stephen Cole likened Shack's playing to that of "a big puppy let loose in a wide field". During the
1965–66 season Shack broke out, scoring 26 goals on a line with
Ron Ellis and
Bob Pulford. His popularity was such that a novelty song called "Clear the Track, Here Comes Shack", written in his honour and performed by Douglas Rankine with
The Secrets, reached No. 1 on the Canadian pop charts and charted for 9 weeks. Playing on the right wing on a line with
Derek Sanderson and
Ed Westfall, Shack's performance rebounded and he scored 23 goals. Afflicted by injuries, he spent the next four seasons moving among the
Los Angeles Kings, the
Buffalo Sabres, and the
Pittsburgh Penguins. Although he was never a big scorer or playmaker, he was able to score 20 goals three more times during these years, including a career high of 27 in 1970–71 in 11 games with Los Angeles and 56 games with Buffalo. Pittsburgh sold him back to Toronto for the
1973–74 season. He retired after the
1974–75 season. ==Post-playing career==