If Fulham's renaissance is a rags-to-riches tale, furnished by the money of Mohamed Al Fayed, then Steve Kean is one if its most heart-warming characters. He is the Celtic reject, groundsman's assistant - and self-confessed glorified taxi driver - who will today pit his wits against the game's most successful manager. Manchester United are in town and Kean will be in the opposition dug-out, in charge, and facing his fellow Glaswegian, Sir Alex Ferguson.

Fulham Assistant Manager Steve Kean

It is said at Fulham that the manager, Chris Coleman, is the man who convinces the players they can run through walls and his number two, Kean, with his tactical nous, is the one who then comes in and suggests ways to get around them as well. Except Coleman has, himself, now been hit by a brick wall. An infection - which has attacked the leg he broke badly in the car accident that ended his playing career - has laid him low. Coleman, still a management rookie, is in hospital, on an intravenous drip, and Kean, another rookie, has stepped up.

Not that he is fazed. It was Kean who devised the 4-5-1 formation that served Fulham to huge effect earlier in the season and who plotted the aggressive approach they took in beating United so arrestingly at Old Trafford last October. They showed no fear. The victory was so comprehensive - and earned with such attacking brio - that Ferguson was unusually effusive.

"If you're getting a compliment about your team from a man of his stature then that's superb," Kean said yesterday. "And we fed that back to the boys. It's good to know that we're performing against the best and beating them."

It bolstered Fulham's season. It fuelled their belief. And it saw them eventually climb, temporarily, to fourth place in the Premiership. It also convinced Ferguson that Louis Saha was worth spending £12.85m on.

"It'll be good to see him because he had great times here," said Kean who insists there are no grudges. "He's gone. When something like that happens you just have to move on." It is a sentiment shared by Sylvain Legwinski - Fulham captain in Lee Clark's absence - although Saha said yesterday that he is expecting a "tough time" from the fans. A calf injury may rule him out, but Saha added: "Even the fans will see I moved to Old Trafford to become a better player, but I had some good times with Fulham and it will be special to go back."

However, he went on: "The first time I walked out at Old Trafford it was a great feeling. I had been used to playing in front of 17,000 people at Fulham, at United it's nearly 70,000. Believe me, you notice the difference." Not the sort of admission to endear himself to his old club. Interestingly the striker went on to compare Coleman to Ferguson. "He's a younger version in the way he feels about football and the way he acts," Saha said.

Saha's departure has forced a different approach. "The way the team was set up was to provide good service to Louis and he was our top goal-scorer," said Kean. "We've had to change things slightly because he's a fantastic player. We're now set up to provide lots of goal-scoring opportunities not just to one player but to a number of players. So hopefully it'll be a little more difficult to read where we're going to score from."

An indication of that, he said, was the midweek FA Cup victory against West Ham - with three different scorers - which set up another game against United in next weekend's quarter-finals. Kean is clear in what he wants. "To win them both," he says. And that claim is not just positive thinking - even though another of Kean's ploys has been to use the motivational expert Watt Nicoll, whose CV is almost as varied as his own.

Fulham Manager Chris Coleman

Twenty years ago Kean was signed by Celtic. It did not work out. Released, he had spells with Swansea and Coimbra, in Portugal, where he worked under Antonio Olivera, who eventually became the country's national coach. His enthusiasm was fired. He returned to England and joined Reading, helping the groundsman and ferrying players around during the day and working with youngsters in the evening. Eventually he became the club's Academy director and was poached four years ago to fulfil a similar role at Fulham. There he succeeded Alan Smith, who was Coleman's manager at Crystal Palace in the early 1990s and is still a close friend.

When Coleman surprisingly got the manager's job it was thought he would appoint Smith as a senior adviser. Instead the Welshman, just 33, poured his faith into 36-year-old Kean. It worked. The two ambitious, hungry young men feed off each other. Coleman has the drive and the "man-management skills", according to Kean. Insiders say he has the "football brain".

"Chris has been sadly missed as far as his contact with the players," said Kean who explained that Coleman had woken up at 4am on Tuesday "feeling as if he was coming down with flu". It got worse and he was hospitalised. "He's had a bit of trauma in his leg because of the car crash," Kean said. "But we think the virus in now under control. He's been up and about and had a few minutes on his legs. So he's not totally out of it."

The two have spoken "before and after" each training session and picked the team at Coleman's hospital bed. "We're in a nice pattern," said Kean of how the players are shaping up. "We've done our training and we've spoken tactically about what we want to do."

There was "shock" when the team was informed of Coleman's condition - just before the cup-tie - but that quickly turned into determination. "The spirit is fantastic and out of a negative, which this is, it's tested. We'll pull together. As soon as you mention it's Chris and we want to give him a tonic, it was very plain to see that they wanted to get a result."

Coleman has been visibly frustrated of late. Lacklustre performances have seen Fulham fall to a still respectable ninth while he has accused players of slipping into a "comfort zone". Kean agreed - "we were in a bit of a rut" - but insisted the manager has not been pushing himself too hard. "It wasn't that he was feeling unwell and that he kept dragging himself, pushing himself on to the training ground," he said. "It [the infection] seemed to be sitting dormant in his system and all of a sudden it's flared up. I wouldn't say he's overdone it." Kean added: "He didn't follow the West Ham game - he was sleeping on and off. We took him up a little bit of footage. But we only took the good bits!"