Ajax head coach Frank de Boer has admitted that he is concerned about reports linking Jasper Cillessen with a move to Manchester United.
Louis van Gaal worked with Cillessen during his time with the Dutch national side, and United will reportedly make a move for him should David de Gea join Real Madrid this summer.
Despite not yet receiving an offer for the 26-year-old goalkeeper, De Boer claims that Ajax could find it tough to keep one of their key men.
"We want to keep Cillessen but if Manchester United decide to pay a certain amount for our keeper, then we are facing a big problem," the Ajax boss told reporters.
"Do I get nervous about this situation? I don't get nervous easily, but in this case I can see a real danger for my club."
Cillessen joined Ajax from NEC Breda for just over £2m in 2011.
