Together with Josef Vacenovský, he reached the quarter-finals of the 1980–81 UEFA Cup with Lokeren, and was vice-champion of Belgium, placing second behind Anderlecht in the 1980–81 Belgian First Division.
[3] His discoveries, brought from his former club Beerschot to Ajax, include Thomas Vermaelen, Toby Alderweireld, Tom De Mul and Jan Vertonghen.
Lokeren, led by Haesaert and Vacenovsky, surprisingly finished fourth in the Belgian First Division, giving the East Flemish club a European ticket.
In his second, and first full season at Beringen, Haesaert brought the club back to the first division, by placing fourth in the championship and then winning the promotion round.
He introduced new training techniques so that the smaller Waregem in terms of budget could still compete with the bigger clubs.
Players like Danny Veyt, Philippe Desmet, Alain Van Baekel and the brothers Luc and Marc Millecamps became the banners of the successful Waregem.
After a short period without a club, he was introduced in the summer of 1990 as the new manager of Germinal Ekeren, replacing René Desaeyere.
Together with players such as Philippe Vande Walle, Mike Verstraeten, Didier Dheedene and Eddy Snelders, he formed the basis for the successes that the club would achieve in the late 1990s.
After his dismissal from Eendracht Aalst, a few clubs again offered themselves, but Haesaert decided to quit as a football manager.
Notable examples include Thomas Vermaelen, Toby Alderweireld, Tom De Mul and Jan Vertonghen.
[8] Haesaert had also advised Ajax to get Mousa Dembélé,[8] and had also Kevin De Bruyne and Eden Hazard on his list.
[9] During his time at Anderlecht he was involved with the discoveries of the likes of Youri Tielemans, Dennis Praet, and Leander Dendoncker.