He and Vejle won the 1984 Danish championship trophy, and he scored his only international goal, in a 1986 World Cup qualification game against the Republic of Ireland in November 1985.

In the winter 1985, Sivebæk moved to England to play for Manchester United, joining fellow Dane Jesper Olsen.

In 1987, Sivebæk was told he would not be a first team regular at Manchester United,[1] and he moved to French club AS Saint-Étienne.

He took part in the final, but suffered an injury and was substituted in favour of Claus Christiansen, and watched from the bench as Denmark won 2–0.

He ended his national team career later that year, following the 1994 World Cup qualification game against Northern Ireland in November 1992.