The Serbian winger joined the Belgian outfit on a loan deal on deadline day, despite Swansea City having previously come to an agreement with the 23-year-old and Liverpool earlier in the afternoon.
His time on Merseyside has been one of frustration, with loan stints in Portugal, Turkey and Hull City last season. Markovic spent the first half of this season on the margins at Melwood, training regularly under Jurgen Klopp but failing to make a first-team appearance.
The £20million signing will hope his move to the Jupiler League will kickstart his career in time for the World Cup this summer, but his new boss has revealed he is someway short of match fitness, having been sidelined for so long.
"I think we will be without him for four, maybe five weeks," Vanhaezebrouck told Nieuwsblad.
"He has a very big gap and in his current condition he is not yet ready to play - there is a lot of work to be done before he can.
"We all hope that he can make rapid progress. He can play in different positions, but he has to get up to speed quickly."