The left winger split his junior career between the Oshawa Generals and the Hamilton Fincups. He scored 79 points in his second year. Combine that with his size and the Buffalo Sabres were impressed enough to make him their first pick, 33rd overall, in the 1976 Amateur Draft.
Kowal would have injury problems in his first two years of pro, particularly a bad knee. He would spend most of his time in the minor leagues, but was called up for 22 games with the Sabres. Kowal scored zero goals and five assists in that time. He also got into two Sabres' playoff games in 1978.
Kowal was quickly buried in the Sabres system. He would play in the minor leagues with several teams before retiring in 1981.