You wouldn't think it now, but for many years Roy Keane was the embodiment of Sir Alex Ferguson on the football pitch, their relationship more akin to father and son than the normal manager-captain partnership.

Keane was Ferguson's eyes and ears in the dressing room, on the training ground and in every match, big and small.

For that reason alone, he deserves to be included in the list of top-10 stars Ferguson had at United. But where does he rank?

Roy Keane enforced Sir Alex Ferguson's iron will on the pitch at Manchester United from 1993-2005

Keane (left) speaks with Ferguson (right) at the Irishman's 2009 testimonial at Old Trafford

10) BRYAN ROBSON (at Man United 1981-1994)

Robson didn't collect the medals the rest of Fergie's big-hitters did – United's success came largely too late for him. But he was the role model that the Class of '92 aspired to be, with Nicky Butt and Ryan Giggs particularly in awe of Captain Marvel, who always had time to educate the younger players on what it took to be a Manchester United player.

Ferguson has never had any doubt that 'Robbo' was one of his greatest players at Old Trafford. When the other heavy drinkers in the United squad - such as like Norman Whiteside and Paul McGrath - were allowed to leave, there was no question of Robson following suit – he was too good.

He was also the first United captain to lift silverware under Ferguson, and was outstanding in the 1990 FA Cup final against Crystal Palace and European Cup-Winners Cup victory over Barcelona the following season.

Bryan Robson (centre), celebrating a 1993 goal with Ryan Giggs (left), is a role model for some United greats

'Captain Marvel' Robson (left) walks arm-in-arm with Ferguson after their 1990 FA Cup final victory

9) GARY NEVILLE (at Man United 1992-2011)

He represented the Manchester in Manchester United, a devoted Reds fan growing up in Bury, Greater Manchester about eight miles north of Old Trafford and not letting any new signing – whether they were from Salford or South America – forget what standards were expected.

Even before Neville was the club's official captain, he did all the organising among the players, whether it was team outings or having them represent the club at a charity or community function.

And let's not be too dismissive of his playing career. He was the epitome of Ferguson's demand that each player should get the absolute maximum out of their ability. By becoming English football's most successful defender, Neville certainly did that.

Gary Neville made sure new signings knew what it meant to be a Manchester United player

Neville made it his business to make new players, such as Wayne Rooney (right), feel welcome at United

8) PETER SCHMEICHEL (at Man United 1991-1999)

Apart from having fights with Roy Keane and waking up Sir Bobby Charlton, Peter Schmeichel was an outstanding goalkeeper, probably the best in the world when he was at Old Trafford. The Great Dane saw himself as captain of the defence and made United's first great team so hard to beat.

His performances in the 'you'll never win anything with kids' season of 1995/96 will never be forgotten at Old Trafford, particularly the effective title decider at Newcastle where he stopped a barrage of shots before Eric Cantona scored the winning goal. And how else should a player leave Manchester United other than clutching the Champions League, as he did in 1999.

Peter Schmeichel was probably the best goalkeeper in the world during his time at Old Trafford

The 'Great Dane' makes a spectacular save in a 1-0 win against Tottenham during the 1994 season

7) WAYNE ROONEY (at Man United 2004-present)

One of Ferguson's best players who ended up not liking him – something of a recurring theme – but Rooney still has the utmost respect and if he goes onto break Manchester United's all-time goalscoring record, it will be Ferguson who helped get him there.

Ever since he announced himself at Old Trafford with a hat-trick against Fenerbahce on his United debut as an 18-year-old, Rooney has been box office news, just like his club. The season following Cristiano Ronaldo's departure, he was absolutely magnificent, the team's talisman.

If he hadn't injured his toe against Bayern Munich in the spring of 2010 and rushed back to play in the second leg, causing more damage, who knows what he would have achieved? He has been very good since then, but beforehand he was truly great.

Wayne Rooney, now United's captain, is one of several top players whose relationship with Fergie soured

Rooney takes orders from Ferguson during a match against Southampton at Old Trafford in January 2013

6) DAVID BECKHAM (at Man United 1992-2003)

When Ed Woodward does all his various global commercial deals from watch manufacturers to global noodle partners, he should give a silent thanks to Beckham on every one.

Beckham's worldwide fame helped make Manchester United genuinely the biggest club on the planet. In every continent, he was the most famous Englishman since The Beatles and United benefitted on his coat-tails.

Even without the celebrity, he was a very important part of the great Ferguson team that ultimately won the Treble in 1999. His goal from the halfway line against Wimbledon in 1996 signalled the United motto that anything was possible.

His shift from the right-hand side to the centre of midfield in the 1999 final against Bayern Munich to cope with the suspensions of Keane and Paul Scholes underlined the faith Ferguson had in him, until he thought his pop star lifestyle was damaging his team ethic, and he went to Real Madrid to become a galactico.

Brand David Beckham was significant in United's global success, but shouldn't detract from the player

Beckham unleashes one of his famous free-kicks in United's 1999 Champions League final win over Bayern

5) ROY KEANE (at Man United 1993-2005)

He used to scare the living daylights out of his team-mates so you can imagine what he did to the opposition. And Ferguson loved it. The pair shared a manic need to win. If it meant harassing referees or treading on people – literally and metaphorically – then so be it.

Ferguson used to trust his captain implicitly and Keane responded. His performance in the 1999 Champions League semi-final against Juventus - when he knew he would miss the final through suspension - was the definition of being a team man.

What Keane didn't realise until too late is that Ferguson was also a pragmatist, while Keane was more of a zealot. When Sir Alex decided Keane the player was no longer worth the aggro, he got rid of him. And Keane has never forgiven him.

Keane (left) with Eric Cantona (right) during a 2-0 win over Everton at Old Trafford in the 1995-1996 season

Keane's effort against Juventus in the Champions League semi in 1999 showed him as an ultimate team man

4) PAUL SCHOLES (at Man United 1993-2011, 2012-2013)

You could argue that over a long period of time, Paul Scholes has been the best United player of all-time, even though his quieter personality has often stopped people using the term 'great' about him.

From Ian Wright to Sir Bobby Charlton, there are many people at the elite end of football who say Scholes is the best they ever played with or saw.

United were always an attacking team under Ferguson and Scholes was the heartbeat of their attacks, choosing the right pace at the right time to get the team moving forward, and also possessing a wonderful shot, packed with power and technique.

He is probably the one player from the last 25 years, United will find it impossible to adequately replace.

For some, including Ian Wright and Sir Bobby Charlton, Paul Scholes is Manchester United's greatest player

Scholes, the heartbeat of United's attack, scores against Barcelona in the Champions League in 2008

3) CRISTIANO RONALDO (at Man United 2003-2009)

Ferguson always said Manchester United had to be the best, the very best. So as the only United player to have officially been the best – voted World Player of the Year in 2008 when he was at Old Trafford – Ronaldo deserves special recognition.

It seems funny to look back and remember that when he signed as a teenager to fill the daunting boots of David Beckham in 2003, he was a regarded as a one-trick show pony, who would do a quick step over and fall to the ground looking for a free-kick.

How he proved everyone wrong. He destroyed Millwall in the 2004 FA Cup final – still United's last win in the competition – and four years later bagged 42 goals as arguably Ferguson's best team won the Premier League and a second Champions League. And of course he scored in the European final against Chelsea with a typically brave and athletic header.

Cristiano Ronaldo won World Player of the Year in 2008 when he was at Old Trafford

Ronaldo celebrates after scoring in United's 3-0 FA Cup final win over Millwall in 2004

Eric Cantona holds the 1992-93 Carling Premiership trophy from his debut season at United

2) ERIC CANTONA (at Man United 1992-1997)

Would United have become the force that dominated English football without Cantona? We will never know for sure but it's surely the best £1million Ferguson ever spent when he signed him from Leeds United in 1992. Had Ferguson paid 50 times the amount, it would still have been a bargain for what he helped the club achieve.

Cantona brought a strut and confidence to United that took them from challengers to No 1. He ensured people could call Old Trafford the Theatre of Dreams without it feeling ham-fisted.

Cantona, with his collar turned up, walked and talked like a leader. And the younger players, particularly David Beckham, soaked it all up. When they looked and saw Cantona in the dressing-room, they felt they couldn't lose.

The influence of Cantona was seen in the 1995-96 season when he returned from suspension to lead United to the league and FA Cup Double. Of course, he scored the winning goal against Liverpool at Wembley in the 'White Suit Final'. United fans still chant his name.

Cantona brought a swagger and confidence to United after his bargain £1million move from Leeds

Cantona (left) is mobbed by his team-mates after scoring the winner in the 1995-96 FA Cup final

1) RYAN GIGGS

Roy Keane famously left Giggs out of his all-time Manchester United XI, saying having a great career didn't make the Welshman a great player. We'll put it down to bitterness on Keane's part because Giggs won 34 trophies under Ferguson and we don't think the United manager would have kept on picking him for 20 years out of charity.

Giggs had just turned 13 when Ferguson, in his first year at the club, persuaded him to pick United over City. It is simply amazing to think that almost 27 years later when Ferguson left, Giggs was still playing in the first-team.

The statistics show Giggs played more times for United than anyone else (963), won more league titles (13) and is the only player to appear in both finals when Ferguson won the Champions League in 1999 and 2008.

He developed from teen idol to elder statesmen and nothing happened at Old Trafford under Ferguson without Giggs being there. Nobody else can claim that and that's why he is No 1.

Ryan Giggs won 34 trophies with United and appeared 963, making him No 1

Keane left Giggs out of his all-time Manchester United XI saying a great career didn't make a great player