Paul Merson believes Jose Mourinho is the "only man" for Manchester United if they want to challenge for the Premier League title next season.
With Louis van Gaal at the helm, United are outsiders to finish in the top four heading into the final day of the season, although they do have an FA Cup final to look forward to on May 21.
Van Gaal has a year left to run on his deal at Old Trafford but there have been reports in Italy that Mourinho has agreed to replace the Dutchman in the summer.
Asked whether he thinks Van Gaal will still be there if United miss out on fourth, Merson told Sky Sports Now: "I think that will be it, he will be gone, and Jose Mourinho will be the next manager.
"If they want to get anywhere near where they want to be, they need to do it quickly, and there is no manager that can do things quickly like Mourinho.
"His impact is very quick and that's what United want. Van Gaal has a year left on his contract and if you keep him and then three months into the next season he is not doing well then whoever comes in takes over a struggling team, that's no good.
"The change needs to be made now, Jose Mourinho is the only man for Manchester United, the only man who can bring quick success."
While Van Gaal's future remains under scrutiny, Roberto Martinez was sacked on Thursday after a below-par season with Everton.
The Toffees are 12th in the Premier League ahead of their final match against Norwich.
While Merson says their league position is not good enough and the players must take some of the blame, he added: "Martinez is a manager who could manage Barcelona.
"He plays a type of football that doesn't suit the Everton fans, they want action and if he went to Barcelona he would be a success. They want playing out from the back and he is very good at that."