Of
Swedish descent, Sponberg had a successful club career, winning three grand finals with two different clubs. A Canterbury junior, Sponberg made his debut for
Western Suburbs in Round 6 of the 1932 season. He played for Wests for three seasons between 1932 and 1934. Sponberg played in the final against
South Sydney after a semi-final win against
Balmain. However, as minor premiers, Souths were allowed right of challenge, and so a rematch of the grand final was played a week later. Western Suburbs lost the grand final 12-19 and Souths took their 11th title. He scored his debut try in round 11 of the 1932 season in a win against
Sydney University. Sponberg played lock in the
1934 Grand Final, with his team defeating
Eastern Suburbs 15-12. He joined the newly admitted
Canterbury-Bankstown club for their debut season in 1935. He played eight seasons with Canterbury between 1935 and 1944, including the
1938 Grand Final and the
1942 Grand Final. He spent the 1940 season as captain-coach of Wollongong, before returning to Canterbury in 1941. In round 4 of 1941, Sponberg scored two tries against South Sydney. In Canterbury's season rematch with Souths, Sponberg also scored two tries to help his team win 16-13. In 1944, Sponberg played his final career game in round 8 against
Newtown. He scored a try in that game. ==Representative career==