Van der Sar told The Overlap, brought to you by Sky Bet: "I worked with Andre Onana for three or four years at Ajax. He came in as a third-choice goalkeeper and was very eager to step up and become the first choice. I thought, and I still think, that he has tremendous qualities – reflections and his feet – but somehow, he has the odd mistake in him that makes you think 'That’s crazy, how can he do that'.
"A team wants stability, to know what your goalkeeper is doing so the back four can relate and I think that’s what happened [the issue] with André. Manchester United haven’t had stability for the last six or seven years – the back four changing, the centre-halves and midfielders changing, coaches changing – so, it’s difficult for new players to come into an environment where the expectations are high, not only for goalkeepers but also for a winger or midfielder. A lot of players who have come here in the last eight or nine years have not reached the level that people expected them to reach.
"I absolutely thought that he [André] would succeed when he first came here. As I said, I worked with him and saw him at Ajax, he did well in Italy and played in a Champions League final, so I thought it was a match made in heaven."