Sir Bobby Charlton is "absolutely certain" Manchester United were right to appoint David Moyes as manager.
United legend Charlton concedes the Premier League champions, who face Manchester City on Tuesday, have played "really, really badly" this season.
But the 76-year-old insisted: "It doesn't mean we are going to change everything. I'm absolutely certain that we picked the right man."
United are seventh in the league with only eight games left.
They lie 11 points adrift of Arsenal in fourth and 18 behind leaders Chelsea, though they are in the quarter-finals of the Champions League.
They can make up some ground if they beat Manchester City at Old Trafford, but are unlikely to finish in the top four this season.
"We are trying our best to make sure that we can beat them," said Charlton ahead of the derby.
"If we can, it will be a tremendous stride because we've had a bit of criticism leading up to this, but I never doubt Manchester United."
Former United and England midfielder Charlton was one of the famed Busby Babes and made his league debut against Charlton Athletic in October 1956.
Charlton left the club in May 1973 having made 758 appearances, winning three First Division titles, an FA Cup and a European Cup, scoring twice in a 4-1 win after extra time against Benfica at Wembley in 1968.
He also played 106 times for England and appeared in four World Cups, having a key role when England won the tournament in 1966, beating West Germany 4-2 after extra time in the final.
Charlton, who is in Malaysia for the Laureus World Sports Awards, said part of him was "glad" he would not be at the game because he gets "too excited" at derby matches.
"I always try to keep myself together when I'm in the directors' box, but sometimes I have to get on my feet," he said. "That is one of these occasions."
Writing in Tuesday's match programme, Moyes insisted United would soon be fighting for the title again.
"Football is cyclical and it will not be long before we are on the up," he said in United Review.
"At this present time we sit behind City in the Premier League table, but that is something we will be looking to rectify in the future.
"The title race is something we are aiming to be involved in over the coming campaigns, just as we have been in the past."
The Scot, who replaced Sir Alex Ferguson last summer, added: "Until it is impossible for us to qualify for next season's Champions League with a top-four finish, we will continue to try and reach that goal."