Manchester United are already prepared to move on without goalkeeper David De Gea, as he sat out of the team’s season-opening win against Tottenham Hotspur.
De Gea has expressed his desire to move to Real Madrid, and the Liga BBVA club are interested in signing him.
Man United are holding out for a £35 m offer though, as they consider that to be De Gea’s true value.
Meanwhile, Cillessen is being valued at £25 m by Ajax, but the Red Devils are confident that they can land the 26-year-old.
Van Gaal previously worked with the Dutch international goalie during his time as Ajax manager between 1991-97, before leaving for Barcelona.
De Gea has also had previous experience in La Liga, which makes Real Madrid an even more intriguing option for the current Red Devils No. 1.
Man United coach van Gaal ultimately wants to keep the 24-year-old goalie though, even if it means risking him leaving when his Man United contract expires next summer.