The Belgium international started the first two games of the 2013-14 season under Mourinho but was soon dropped to the bench.
He eventually joined Wolfsburg in 2014, but not before Mourinho explained why he was not in contention for playing time.
"But the truth is that I only ever spoke to him twice. The plan was always for me to go on loan for a bit.
He added: "Jose called me into his office in December, and it was probably the second big life-changing moment for me. He had some papers in front of him, and he said, 'One assist. Zero goals. Ten recoveries'.
"It took me a minute to understand what he was doing. Then he started reading the stats of the other attacking forwards - Willian, Oscar, Mata, Schürrle. And it's like - five goals, 10 assists, whatever.
"Jose was just kind of waiting for me to say something, and finally I said, 'But… some of these guys have played 15, 20 games. I've only played three. So it's going to be different, no?'
"It was so strange. I was completely honest. I said, 'I feel like the club doesn't really want me here. I want to play football. I'd rather you sell me.'"