Chris Smalling grew up in a household that in footballing terms was quite a battleground. His mum, Theresa, followed Tottenham. He supported Arsenal. His father, Lloyd, and younger brother Jason plumped for Manchester United. Little did this young Gunner know that one day he would be playing at White Hart Lane, about to meet Sir Alex Ferguson, and that his world would spin upside down in the most thrilling way imaginable.

Sitting in the wintry sunshine at Fulham's training ground, Smalling gives the impression that he is remarkably calm about the recent turn of events that led him to sign for Manchester United. He will move to Old Trafford in the summer, just two years after he left Maidstone in the Isthmian League, six tiers below the top flight. Those promising feet are grounded. There is enough apprehension mixed in with the excitement to prevent any sudden swagger. "It's been a really crazy couple of years," he says, bashfully.

The craziness peaked last month. His career was progressing steadily at Craven Cottage, and Smalling had been selected for his second Premier League start for an away match at Tottenham Hotspur. Nobody said a word before kick-off as Fulham's management team wanted him to be concentrating fully, but afterwards he was pulled aside and informed that Ferguson had come to watch him and wanted to talk to him. Considering that it was the eve of the Carling Cup semi-final second leg, with United preparing to play City at Old Trafford, Smalling was bowled over to discover that the manager of the Premier League champions would make such an effort. Just for him. Up until that point he had played 239 minutes of Premier League football.

"For him to come down the day before a big game was a huge compliment," he says. "That made it feel incredible. I went up the next day to the Manchester derby and got to meet some of the players afterwards. I went to see the training ground, did the medical, and everyone was very welcoming."

The 20-year-old found himself chewing the fat with one of his role models, Rio Ferdinand, a fellow south London boy who told him about moving north at a young age to further his career. "He told me I would very much enjoy it up there," adds Smalling, who returned to London enthusing about how he might pick up some tips from the main man next season and hopefully even play alongside him in the centre of defence.

That treatment worked. The player had been torn when it emerged that his boyhood club, and one much closer to home, was also in the chase. But Arsène Wenger did not put in the personal effort that Ferguson did, a reversal of what happened when Aaron Ramsey was the prize they fought over.

"When Sir Alex came and met me and I went to go up and visit, I had the gut feeling this was the place for me to continue my football education," Smalling says. "My brother was just over the moon. Being a Man United fan he is going to want a few tickets. My mum and brother are so proud of me."

So they should be. Few players make the leap from non-league to Champions League within a couple of years. Not so long ago Smalling was making plans for a life where the idea of football as a career was a hope rather than an expectation. He worked hard at school, and his A-level passes in economics, business studies and media secured him a university place. "I would have gone to Loughborough to study business management and was looking forward to that very much," he says.

While studying for his exams at 17 he was also playing for Maidstone United. He trained twice a week and played matches at the weekend, experiencing a side of football he appreciates for giving him perspective. "My team-mates had different jobs," he recalls. "A few worked in the city, some did building and carpentry, a lot of them had played in the league at a higher level but dropped down for whatever reason, whether they were coming to the end of their career or had an injury and struggled to get back," he says. "That makes you value the opportunity you have."

Thankfully, once he reached the first team at Maidstone he did not have to take his kit home for mum to deal with, but he still had to get himself to matches and cadged lifts from his friends. "Some games would be a bit of a nightmare if there was traffic and you'd be rushing for kick-off. Not the sort of thing you do in the Premier League."

Naturally, as a teenager, he was targeted by the gnarled veterans of the Isthmian League. "Their game is geared to sort of roughing you up if they see they are up against someone who has played a handful of times. That gave me a grounding in the less pretty side of the game. I like to get the ball down and play, but I can always get stuck in and hold my own."

He was picked for England schoolboys, a selection that opened the door to trials with a couple of Premier League clubs, and it was Fulham who felt right in the summer of 2008. "After playing a reserve game Roy Hodgson took me into his office and complimented me on my game. We had a general chat, he was telling me about when he played for Maidstone back in the day, so it all felt very nice to be at the club. They gave me a chance, they saw some raw ability and it has been a joy working here every day."

Smalling is hopeful he can experience some tangible success with his team-mates before he bids them farewell. Fulham has got under his skin, and he would dearly love some cup success, with Tottenham in the FA Cup quarter-finals today and Juventus in the Europa League on the horizon. "The chance of getting to Wembley, and playing against the likes of Juventus, shows how far we have come as a group."

In the meantime, he is juggling plates again. When not focusing on Fulham, he is planning for Old Trafford. He has already started the search for a place to live, and wants to get sorted before the summer so he is ready to hit the ground running in pre-season.

Overall, he could hardly be more sensible. Ferguson knows his £10m has been spent on a player who does not just have the talent to go far, but the work ethic and level-headedness as well. He even wants to continue his studies while he is at Manchester United. "I'd like to pick it up as there is obviously quite a bit of spare time after training, to get a few qualifications for after football."

Smalling has another thing going for him. As he gets up from his seat when our conversation draws to a close, he seems to go on forever. Some footballers are not as big as you expect in the flesh, but Smalling towers. It is necessary to crane your neck to say goodbye and apparently all 6ft 4in of him is yet to fill out. Manchester United just might have bought themselves a very big player for the future.