Ghana midfielder Majeed Ashimeru started for Anderlecht on the opening day of the Jupiler Pro League as they suffered defeat to Union Saint-Gilloise at home.
The midfielder was replaced right after the break with the scoreline at 1-1, as the Purple and White succumbed to a second half defeat.
The visitors opened the scoring after 20 minutes through Loïc Lapoussin, but Anderlecht leveled right at the stroke of half-time, Yari Verschaeren nodded home.
But the Belgium giants fell apart in the second half, conceding twice to lose at the Constant Vanden Stadium.
Deniz Undav shot Union Gilloise in the lead after the hour mark, before Lzare Armani sealed victory in the 73rd minute.
It is unclear why Ashimeru was subbed after 45 minute, but the decision looked to have cost Anderlecht as they struggled in the middle.
The former Belgium champions will next travel to KAS Eupen.