Gary Neville believes Louis van Gaal's greatest achievement as a football manager is the making of Jose Mourinho. Van Gaal and Mourinho come face-to-face on Saturday when the former's Manchester United travel to Premier League leaders Chelsea. The duo have been friends since they first worked together at Barcelona in 1997 where they enjoyed a successful relationship at the Camp Nou. Louis van Gaal's (right) greatest achievement in football is the making of Jose Mourinho, feels Gary Neville . Mourinho (left) and Van Gaal will come face to face again when Chelsea host Manchester United on Saturday . Mourinho (left) worked under Van Gaal as his assistant manager at Barcelona for three years in 1997 . With Mourinho as the Dutchman's assistant, they won the La Liga title twice in their first two years together in Catalonia. It was Van Gaal who entrusted and encouraged the Portuguese to go into management - with the 52-year-old having won titles in Portugal, England, Italy and Spain since as well as the Champions League twice. And in his column for the Telegraph, Neville says Van Gaal will be proud of his friend's achievements. 'A former Tory leader once said when asked what their greatest achievement was: "New Labour," the former United and England defender wrote. 'I can imagine Louis van Gaal, when answering the same question from a group of journalists, peering back from his desk and responding: "Mourinho".' Ahead of Saturday's clash at Stamford Bridge United have been dealt a quadruple injury blow with the news that Phil Jones, Michael Carrick, Daley Blind and Marcos Rojo will all be unavailable. Van Gaal though will be able to call on the services of the in-form Marouane Fellaini. The Belgian midfielder has scored twice in United's last four league games - including a header in their 4-2 derby win over rivals Manchester City on April 12. Marcos Rojo (right) is one of four United players who will miss their league trip to Chelsea due to injury . The Red Devils have in-form midfielder Maraoune Fellaini (left) available for the trip to Stamford Bridge . Fellaini (right) scored United's second goal in their 4-2 win over Manchester City on April 12 . And Neville believes Mourinho may try to nulify the threat of the big Belgian midfielder by selecting John Obi Mikel or Kurt Zouma in midfield. Neville added: 'As for Mourinho, will he blink and deploy John Obi Mikel or Kurt Zouma in midfield alongside Nemanja Matic to deal with Marouane Fellaini in that dangerous United left channel? 'If he does, how will his team get hold of the ball without the rhythm of Cesc Fabregas in that deeper role and feed an attack already hit by the loss of Diego Costa? I could see United having 60 to 65% of the ball if Mourinho does opt for this solution. 'As a tactic, this wouldn't ordinarily worry the Chelsea manager, but the idea of Van Gaal going to Stamford Bridge and not only winning, but also dominating the ball, would maybe open up the wounds of his early encounters with Barcelona while coaching Real Madrid, when the Barca purists outplayed and beat his team well. I’m also pretty sure it would not be something that Roman Abramovich would enjoy. 'My hope is that they go for each other in a manner which suggests that both feel that they are superior in the football department.' John Obi Mikel (centre right) could start in midfield for Chelsea in a tactic to nullify the threat of Fellaini .
Chelsea entertain Manchester United in the Premier League on Saturday.
Chelsea boss Jose Mourinho and United manager Louis van Gaal are pals.
Pair enjoyed a successful relationship together at Barcelona in the 1990s.
Mourinho has since won trophies in Portugal, England, Italy and Spain.