Manchester United's triumph over Chelsea in a desperately close title race was not just down to one man. Too many others played their part at vital times for that to be the case.

But if you are looking for the single biggest reason why the trophy is staying at Old Trafford, then an individual has to come to the fore - Cristiano Ronaldo dos Santos Aveiro.

The Portuguese maestro's 31 league goals did not just make him only the fifth man in Premier League history to reach the 30-goal landmark. They also proved crucial in helping Sir Alex Ferguson's men finish top of the table - Chelsea simply did not have a goalscorer to match.

Whether United deserved their success for their more stylish approach can be debated. But the fact they earned more points and scored more goals cannot and as his side's top marksman, Ronaldo undoubtedly made the difference.

With the Champions League final still to come, he has already hit 41 goals in all competitions for his club so far over the course of a prolific campaign - a tally only bettered at United by Ruud van Nistelrooy and Denis Law.

Ronaldo also managed three for his country this season (part of an overall personal tally of eight in Portugal's successful Euro 2008 qualifying campaign) to enhance his iconic status in his homeland.

Fast and full of tricks, the 23-year-old has menaced defences since he arrived from Sporting Lisbon in 2003. But in his early days in England he managed more step-overs and dubious dives than goals or assists.

That is no longer the case as Manchester City and England defender Micah Richards, one of the few men to have kept Ronaldo quiet this season, told BBC Sport.

"The best thing about Cristiano now is his finishing," said Richards.

"Every time he has a chance he seems to put it away and that is the biggest difference between this season and previous ones - he has got that end product now.

"He used to be all about dribbling but he does not really do that so much anymore. He just gets in the right positions to allow him to run straight at defences.

"There are areas in every player's game where they can improve - but the thing about the best players is that they have consistency and Ronaldo has shown that this year."

Many of Ronaldo's goals from this extraordinary season will live long in the memory, but it is his free-kick against Portsmouth in January that really stands out, an exocet of a shot that dipped into the top corner and left Pompey keeper David James helpless.

His technique in generating top-spin when shooting from set-pieces - a new string to his bow this season - is something special.

And it is the fact that Ronaldo continues to add these attributes to his game that has impressed Blackburn keeper Brad Friedel the most.

"In my opinion he is the best player in the world," Friedel told BBC Sport.

"Every so often, the top players just go through periods where they are in the zone and he is in one at the moment. But not only that, he is a tremendous professional who keeps coming up with something new.

"In November he scored twice against us. One was a header after we failed to man-mark him at a corner and the other was on a counter-attack.

"We played them again in April and in that time he developed that new free-kick of his."

When it comes to keeping Ronaldo quiet, Richards and Friedel both agree on one thing: it is not easily done.

If you are defending against him, do you mark him closely, try to stop him running at you, or cut off his supply?

"All of the above," Friedel suggested. "But some luck goes into it and it depends how the game is panning out.

"If you let him have time and space to run at you with the ball and you keep backing off then he will kill you.

"You have to try to impose yourself on him as high up the pitch as possible but I am not saying it is easily done."

Ronaldo missed United's defeat by City at Eastlands in August through suspension after he was sent off for a head-butt against Portsmouth in the second game of the season.

And he was subdued in the return at Old Trafford in February as City claimed a shock 2-1 win.

"We went out to play our game but we knew we had to stay tight to him because he could hurt us," Richards added. "It was definitely a tactic to challenge him as early as possible.

"There is still a way of stopping him, same as every player, but when he is having a season like he is doing, then it is hard to do."

You can count the poor games Ronaldo has had this season on one hand and Ferguson's decision to give him a free role is a major factor behind his magnificent form.

But just as important is the way the entire United side is set up to get the most out of him and his fellow front-men Wayne Rooney and Carlos Tevez.

"A lot of how good Cristiano is down to how successful United are as a complete team unit," said Friedel. "They can attack with five or six players and are an exceptional side going forward.

"They interchange positions so frequently that it is difficult to call one player an out-and-out striker or midfielder.

"When they go forward they are the most difficult team to play against right now. Chelsea are more machine-like - they will grind out results whereas United will run over you."

When United are in full flow, Ronaldo has inevitably been their fulcrum, hence his deserved double in the Professional Footballers' Association and Football Writers' player of the year awards.

Yet nagging doubts persist over his performances in the crunch games. However often he has destroyed average sides, he still needs to become the conqueror of a brilliant one.

"Whenever someone is doing well, somebody will put them down," Richards added. "But I suppose that is where you separate the man from the boys.

"He has scored a lot of goals against the lesser teams in the Premier League but he will be judged on what he does on a bigger stage.

"He has got Euro 2008 in the summer and we will see what happens then - when you have one of the best players in the world in your side then you expect to do well."

The game in which Ronaldo truly defines the early part of his career could come in Moscow on 21 May or in Austria and Switzerland this summer.

Portugal coach Luiz Felipe Scolari has spent the last few years playing down the importance of Ronaldo to his team.

But Sergio Krithinas of Portuguese tabloid 24 Horas told BBC Sport: "To the fans he is almost the national side on his own.

"Everyone sees that we depend on Cristiano to have a good Euro 2008. He is the centre of every hope that we have, but Scolari is trying not to put too much pressure on him."

But even Scholari has had to start talking about Ronaldo's excellence, telling Brazilian radio station Globo that a Fifa world player of the year title would be richly deserved.

Scolari said: "Cristiano has developed not only as a player but as a person.

"He showed great potential at international level before he turned 18 and he is proving now that he is a great player.

"If he follows this way, growing as a player and as a man, he will surely be considered the best in the world, I have no doubts about it."

The Premier League title is in the bag - but it should be just the start of a memorable summer for Ronaldo.