Roy Keane was the true all-time great in Man Utd's best ever midfield - not Ryan Giggs

A good example is the legendary Manchester United midfield of the late 1990s and early 2000s: David Beckham, Roy Keane, Paul Scholes and Ryan Giggs. When Keane retired, most would have regarded him as the best of that quartet; now that status is held by Ryan Giggs, and many would put Scholes above Keane as well.

When Sky's Soccer Saturday pundits picked their all-time Premier League XI over Christmas, their midfield included Giggs but not Keane. When the Daily Telegraph recently published their list of the 100 greatest Premier League players, Giggs was first, Keane third, Scholes fifth and Beckham an insulting 21st.

A player's status can change during his career, too. During his time at United, particularly during the Treble season, Beckham was often more important to the team's success than Scholes and Giggs, yet now he is by far the least celebrated of that midfield.

Similarly, for most of his career, Keane was regarded as the No1. “If I was putting Roy Keane out there to represent Manchester United on a one against one, we'd win the Derby, the National, the Boat Race and anything else,” said Sir Alex Ferguson in 2002. "It's an incredible thing he's got.”

It's a thing his peers did not have. In a sense it feels churlish to criticise this quartet. They were the last great British and Irish midfield and arguably the best, so perfectly complementary that they could have been put together by boffins seeking the ultimate midfield: put simply, there was the crosser, the ballwinner, the passer and the dribbler. Yet it would also be immature to not observe when sentiment has warped received wisdom, in this case by placing Giggs above Keane.

Part of the problem with such discussions is that the word 'overrated' has excessively negative connotations. It is possible to regard someone as absolutely brilliant and slightly overrated, like Giggs. Yet to criticise someone with his status is seen as sacrilegious.

The peculiar thing about Giggs is that his reputation grew as his performances declined. There is one simple reason for that: longevity. It is a slippery concept; while it is obviously quantifiable, it's also hard to precisely qualify its worth. It is worth far more with great players – just ask Emile Heskey – and rightly prompts a misty-eyed reverence. To play 963 games for Manchester United, as Giggs did, is astonishing. But it would be wrong to confuse longevity with consistency. Giggs and Scholes were not regulars in the side for the majority of their final years like, say, Javier Zanetti. It all depends on how much you value longevity. What is worth more: 480 games of Roy Keane or 963 games of Ryan Giggs?

Or, indeed, 480 games of early Ryan Giggs. There is an argument that he would have been a greater player had he finished in his twenties like George Best, such was his performance level up until then. In essence he had two careers. From 1991-92 to 2001-02, the last season in which he consistently twisted defenders' blood, he was frequently awesome. A mark of his true greatness was the extent to which he terrified European defenders, and particularly Juventus defenders. After that he became more of a squad player, and his role evolved.

The second half of Giggs's career was a strikingly mixed bag. There were some great spells – the winter of 2004-05; a strong 2006-07 season; a staggering performance against Chelsea in 2008-09, which led to his sentimental Player of the Year and Sports Personality of the Year awards; and an exceptional few months at the end of 2010-11 season – yet there were also some big dips of form and listless, entitled performances. He had a number of absolute shockers.

Two of them came in the Champions League finals against Barcelona in 2009 and 2011, when he went AWOL despite being in good form at the time. The fact he created Wayne Rooney's goal in the latter should not disguise a horrible performance. As long ago as 2005, a young Darren Fletcher was selected ahead of Giggs for the FA Cup final against Arsenal, and nobody really batted an eyelid. The same was true when Nicky Butt was regularly preferred to Scholes for the toughest games during United's Treble season.

Keane was never omitted from a big game, not even when the pesky foreigner rule was in place in the European Cup, not even when his legs started to go in his last 12 months at Old Trafford. The matches he did miss, when he was rested, reaffirmed his importance because United often lost stupid games: at home to Middlesbrough in 2001-02, a hugely damaging defeat in the title race, and at home to Fulham in 2003-04 for example. Keane may not be the best Premier League player ever - Cristiano Ronaldo surely takes that honour - but he's certainly the most influential, an endless well of conviction and mental strength from which his team-mates took inspiration. Whereas Giggs' performance level fluctuated wildly, Keane was a monster of consistency who had a profound influence on most games he played. His mean, median and mode performances were significantly higher than those of Giggs and Scholes.

There are multiple reasons why a player's reputation might change in the twilight of his career or after retirement. When we pick an all-time Premier League XI, the lack of credible rivals in Giggs' position as compared to Keane - albeit with a respectful nod to Robert Pires - makes him stand out more. The fact Keane has fallen out so bitterly with Ferguson will consciously or unconsciously colour many perceptions. He is no longer part of the family whereas Giggs and Scholes flout their top-red credentials all the time.

The upshot is that history has been rewritten. It's a personal opinion that it needs to be rewritten again to let the record show that, while Giggs and Scholes were great players, Keane was an all-time great.