Mozambique-born coach Carlos Queiroz is Manchester United's assistant manager and is the fourth assistant Sir Alex Ferguson has had during his 18 years. Queiroz must rank as one of the most widely travelled figures in English football with a vast array of experience, though some will point out his inability to hold down a job for long.

Building up a reputation for working with youth players, he coached the Portuguese U21 to the Football World Youth Championship twice in 1989 and 1991. Queiroz was credited with discovering Portugal's "golden generation" of great players such as Figo, Rui Costa , Joao Pinto and Jorge Costa.

He was awarded the post of manager of the Portugal national team in 1993 though this lasted only a year. Then, he took over at Sporting Lisbon with a move to the USA following in 1996 with the New York/ Jersey MetroStars. Carlos then sampled life in Japan with Nagoya Grampus Eight in 1997 then he was off to the Middle East with the United Arab Emirates national team in 1999.

Following this he returned to his native Africa with the South Africa national team (2000-2002) . Under Queiroz, South Africa strolled through to qualification for the 2002 World Cup but he resigned before the finals began in June 2002 after falling out with the technical director Jomo Sono.

A well respected name in World football, Carlos' arrival at the start of season 2002-2003 was a factor in United's successful title win. His tactical and training expertise worked well alongside Sir Alex who had gone without a deputy since the departure of Steve McClaren.

He was credited with re-organising the defence to catch Arsenal and claim the title whilst Roy Keane sung his praises loudly. Queiroz's relationship was likened to the one Ferguson had with Steve McClaren, his instincts being on the technical and scientific side, which the United manager lacked.

The partnership worked too well in fact, as Real Madrid were so impressed they wanted him as their coach to replace the exiting Vicente del Bosque. It was an opportunity to work with the likes of Figo, Zidane and Ronaldo which Queiroz was unable to turn down. He was appointed only a week after David Beckham's arrival at the Bernabeu in June 2003.

However, his 10 months at Madrid were a disaster and Carlos would go on to join the long list of failures on the Bernabéu managerial scrapheap. Real got off to a sluggish start but rallied mid-season to top the La Liga table. However they contrived to lose their final five matches finish 3rd - and give Valencia the title. The Galaticos had won nothing and Carlos took the flak from the Spanish media and fans. He was duly axed in May 2004.

Reforming the old partnership with Ferguson proved an attractive option to both sides. United had trailed 15 points behind Arsenal and Fergie was forced to bring in temporary help from Walter Smith during the tough end of season run-in. Subsequently, Queiroz returned to United as assistant manager on 1st July 2004, signing a 3-year deal.

It has been documented that Queiroz is responsible for organising the player's training, whilst Sir Alex takes a back seat. In fact Queiroz takes training, works on tactics for the next game, sometimes announces the team and increasingly deals with media - he handles all BBC media because Ferguson will not speak to them. It perhaps an exaggeration to say he and Ferguson can be called joint managers these days but it cannot be ignored that most supporters are uneasy with this apparent shift in the relationship.

In his days at Old Trafford the Portuguese has been the brunt of criticism. There were rumours that some United players did not enjoy Queiroz's training methods, not to mention the fan's derision at his preferred team formation. Roy Keane disagreed with many of Carlos methods and it was a bitter argument between the two that proved pivotal in the Irishman's Old Trafford exit of 2005.

The 4-3-3/4-5-1 system is largely thought to be the work of Queiroz's and many have blamed him for the abandonment of 4-4-2 that brought so much success in the 1990's. The most frequent criticism was that with Van Nistelrooy (or Rooney) as a solitary striker, the system is far too cautious and goes against United's famous spirit of attacking adventure.

Queiroz doesn't mind the critics who have slammed the system and his own lack of career success, especially after the Real Madrid humiliation. He says "Criticism, for me, is inspirational. The position of the coach is to accept and respect criticism, no matter how tough it is. All professionals, people who expose their lives in public, must accept it".

"The final product is to defend well, avoid goals. If we need to defend with 10 players behind the ball we are going to do that. Those results when you score three, four, five goals, they don't come often." Such an attitude seems at odds with United's philosphy but he can also point to the fact there is hardly a leading team in Europe who stick rigidly to 4-4-2 and that last season United created more shots on goal than any other team in the Premiership.

There can be no doubt a shift of power has occurred in the last two season's as Sir Alex, in his advancing years, has lightened the burden of the job. In the past Ferguson was renowned for his incredible attention to detail and meticulous preparation but he is now prepared to let Queiroz share much of the responsibility.

When results were going badly Queiroz was the scapegoat but in the last season with United reclaiming the Premiership title the critics have been silenced and left him to get quietly on with his job. Fergie has even gone on record as saying he would like him to succeed him as manager at Old Trafford. Whether the Glazer family agrees with him is another matter.