The former Blues hero believes the only way to outfox Jose Mourinho is to attack.
Chelsea manager Antonio Conte’s famed 3-4-3 system was rated as the key to his side winning the title last season.
And Le Saux, who won the Second Division, the League Cup, the European Cup Winners’ Cup and the Super Cup with Chelsea and the Premier League with Blackburn, has urged the Italian to resist the urge to tinker and stick to that system.
“That system that Conte hit upon is a weapon for breaking any team down,” said the former England left-back. “With that system you have got players who can cause problems for any opponent.
“But that only works if Chelsea play high up the field at Wembley and put pressure on United.
“Chelsea’s wing-backs, Marcos Alonso and Victor Moses, will force United’s players to stay deep, and drag their full-backs out of position.
“The key for me is that Chelsea’s outside players, probably Willian and Eden Hazard, play really high up. Then they will get inside United’s full-backs, and they will have real problems.
“Last season Chelsea kept the ball really well when they played high, and their passing was pinpoint. That has not happened anywhere near as much this season – but it has to in this final.
“It would be much better for Conte to play with a front three – say Hazard, Willian and Olivier Giroud – because that will keep United’s centre-backs occupied, and the wide men, who should have loads of space, will challenge their discipline.
“I would play Tiemoue Bakayoko in midfield alongside N’Golo Kante, because Chelsea will need to match United for physicality and running in midfield. Bakayoko has had a tough season but he is young, and he has played better recently.
“Fabregas passes the ball superbly, but he does not cover back as well or tackle, and against players like Paul Pogba and Nemanja Matic in midfield Chelsea are going to need that. They cannot be lightweight in that area.
“Bakayoko was a good player for Monaco last year and you don’t turn into a bad player overnight. He has found it hard to adjust, but I think he will come good.”
Conte has no injury problems to worry about, and with the Italian expected to depart the club after this final, win or lose, he is unlikely to divert from his best team.
Le Saux added: “Both these teams have under-performed this season. Chelsea have been inconsistent, United seem to have been held back, maybe by tactics.
“But there is so much quality out there that this final will be decided by one star player from either side saying, This is going to be my cup final’.
“Chelsea cannot play on the counter attack. They have to play high, they have to take the game to United. That is the way they will win this Cup final.”