A full international between 1972 and 1979, he won 40 caps and scored seven goals for the Sweden national team and represented his country at the 1974 and 1978 editions of the FIFA World Cup.
Torstensson commenced his career with Åtvidabergs FF in southern Sweden, then a club renowned for its successful youth development.
[2] In the first round of the 1973–74 European Champions Cup campaign Åtvidabergs FF encountered Bayern Munich, with stars like Franz Beckenbauer and Gerd Müller one of the favourites of the competition.
He impressed most in European Cup matches, where he scored a number of important goals, and won the competition three times consecutively between 1974 and 1976, featuring in the finals of 1974 and 1975.
On club level Torstensson moved 1977 to FC Zürich in Switzerland, returning a year later to Åtvidabergs FF, where he ended his career in 1980.