But the Belgian defender is confident that his side can still challenge for silverware next season.
“I am disappointed because I wanted him to stay at the club,” he told Sky Sports News.
“He was fantastic for us in the last year, scored lots of goals and I am disappointed he is going, but we have to focus on the next season with Arsenal. We have to fight and I am confident we have a squad to win something.”
“We start Saturday and this is all clear now, Robin is leaving and we have to move on,” he added.
