Former Anderlecht goalkeeper Frank Boeckx has revealed how Percy Tau "hurt the club badly" during Union Saint-Gilloise's famous 2018 victory over the Belgian giants.
Boeckx, who is now a goalkeeping coach at Anderlecht, was speaking ahead of his side's 5-0 Belgian Cup win over the second division outfit on Thursday when he reflected the two sides' last meeting, which ended in a shock 3-0 defeat at the hands of a Percy Tau and Youssoufou Niakate-inspired Union in 2018.
The 34-year-old was in goal for Les Mauves that day in what was one of his final appearances for the club, and jokingly revealed that he avoided talking about the match with Tau, who spent the first part of the current season on loan with the record 34-time league champions.
"I forgot about this match against the Union," he lightheartedly told Derniere Heure and Les Sports. "I also avoided talking about it to Percy Tau, who hurt us very badly with his acceleration. Now we know Union better. We know that we have to take this match seriously, that they are a formidable opponent.
"At that time, we were having a difficult time. And it's true, I made a mistake on the second goal. But I have always been a proactive goalkeeper, I wanted to correct someone else's mistake."
Scroll through the gallery below to see where Tau ranks among South Africa's most valuable overseas-based players
Boeckx then elaborated on the incident in question and attributed the blame to former teammate Alexis Saelemaekers, who has since moved on to join Serie A side AC Milan.
"I couldn't say that publicly then, but now I can: Alexis Saelemaekers was not doing his job there," he added, per Het Nieuwsblad. "He dribbled on the corner flag and failed to maintain his position in midfield.
"I tried proactively to take the counter out, but underestimated the speed of the Union strikers and was seen. If I had said that in the press at the time, it would have been hard for Saelemaekers. I had to protect him and kept my criticism internal. Now Alexis is far enough in his career to hear it: it was his fault."
Tau ultimately scored 13 goals in 35 appearances across all competitions during his time with Union and won the Belgian First Division B Player of the Season award, before enjoying fruitful loan spells with Club Brugge and Anderlecht over the course of the next 18 months.