Manchester United are reaping the benefit of a long-term strategy to invest in young players, assistant manager Carlos Queiroz told BBC Sport.
Man Utd say they are benefiting from faith in Rooney and Ronaldo
He said their return to top form was due to their faith in stars such as Wayne Rooney and Cristiano Ronaldo.
"You cannot perform at this level in a consistent way if these players are not mature and ready to compete," he said.
"We knew sooner or later the results would come up if we kept going with patience, stability and continuity."
Queiroz said United's success this season was the fruit of plans laid by manager Sir Alex Ferguson in the last two seasons.
And he said Ronaldo, whose conversion from unfulfilled talent to one of the most destructive players in the Premiership has been at the forefront of United's resurgence, was an example of how the strategy had worked.
"[It's] continuity, daily work, being patient with mistakes, being on the right track, believing that if we trust them and if we provide them with the right preparation that sooner or later they grow up and they start to perform," Queiroz said.
You must give the opportunity for young players to play, learn the game, gain experience and mature
Man Utd assistant manager
"And this is exactly what happened."
Queiroz, who earlier this week said Ronaldo had "no reason to leave" United this summer despite interest from Real Madrid and Barcelona, added: "What we are doing this season is the natural progression of everything we have done in the last few years."
That has meant melding the increasing maturity of the younger generation of players - which he said also included midfielders Darren Fletcher and John O'Shea and defender Wes Brown - with the experience of established stars such as Ryan Giggs, Paul Scholes and Gary Neville.
He said the fact that United had flourished despite selling lead striker Ruud van Nistelrooy to Real last summer was proof that Ferguson's strategy was correct.
"Those decisions - one in, one out - are one thing. And of course they can interfere. But in this moment they are a minor part of the overall plan of the club," Queiroz said.
"The other thing is the core of the group, the structure, the tactical concept, the harmony between the players, the tactical knowledge, making the young players grow up to be more mature, more knowledgeable of the game.
"Then you add different solutions, buying or selling. But that part of the team is the easiest part. This is what everyone can see.
Man Utd have successfully blended youth and experience
"Of course, when you lose a player who used to score 30 or 40 goals a season, theoretically it is a concern.
"But when that decision came up it was important to be sure that the team and structure didn't suffer with that. And we just kept going because the manager thought we had the right solution.
"It was our belief that some of the problems we had during the [last] season were not related to a, b or c.
"It was part of the main decisions we've been doing - giving the opportunity for young players to play, giving the opportunity for them to learn the game and gain experience, to mature."
United last won the title in 2003, but were third in the following two seasons behind Arsenal and then Chelsea.
United had appeared in the last two seasons to be struggling to keep pace with Chelsea under Jose Mourinho, who beat them into second place with a margin of eight points in 2006.
But this season Scholes has returned to full fitness after being out for much of 2005/6 with an eye problem, Ronaldo has enjoyed his best season, striker Louis Saha started strongly and veteran Swede Henrik Larsson joined in the new year on loan to bolster the team up front.
That successful blend of youth and experience has led to United being six points clear at the top of the table.