United won 1-0 at home to Aston Villa on Saturday courtesy of Marcus Rashford's seventh goal in 12 games but the one-paced football and lack of entertainment caused more exasperation among worried supporters.
If Van Gaal triumphed in the Cup, it would offer the opportunity to head into retirement on a relative high if United opted to dispense with his services but the Dutchman does not believe his superiors have made a definitive decision yet and thinks results over the next few weeks could still on a bearing on his future.
Despite his calamitous last season at Chelsea, when he was sacked in December seven months after winning the title with the club one point above the relegation zone, the prospect of Mourinho taking charge at Old Trafford would be tantalising in many respects, not least because it would see a renewal of his rivalry with Pep Guardiola. Guardiola, who succeeds Manuel Pellegrini as Manchester City manager in the summer, was in charge of Barcelona when Mourinho managed the Catalan club's bitter rivals, Real Madrid.
United are interested in signing Renato Sanches, Benfica's gifted young midfielder, and Everton centre-half John Stones this summer and they are targets Mourinho fully supports. Mourinho made a series of failed bids for Stones when at Chelsea and also tried and failed to bring Sanches to Stamford Bridge. Zlatan Ibrahimovic has admitted he would happily play under Mourinho at United with the club also weighing up a move for the Sweden striker, who is out of contract at Paris St-Germain at the end of the season.