For the latter he scored a total of 69 goals in 106 appearances and had an effective partnership with Norway's Hallvar Thoresen in the mid-1980s.

He began his career at the local pride BV Veendam, breaking into the first-team squad in 1978.

He adapted quickly to the top-tier professional level and, over two and a half years, missed few matches.

After continuing to play on FC Groningen, Vitesse Arnhem and De Graafschap he ended his career where it had once started, with BV Veendam.

Koolhof was fired from his job on 19 February 2007 due to disappointing results, strikingly on the same day Cambuur Leeuwarden let go their trainer Roy Wesseling.

On 15 March the 47-year-old Koolhof signed a two-year contract at SC Cambuur-Leeuwarden, taking effect 1 July 2007.

His spot was taken by Alfons Arts, who became Koolhof's assistant manager as well as a youth trainer.