LONDON • A 1.93m, quick and sleek Chris Smalling always had the look of a Rolls-Royce defender. But it is what one cannot see that has underpinned his blossoming into England's best centre-half.

A suspicion that one still underestimates the psychological dimension is heightened over discussion with Smalling, who talks about how mental application lies behind his outstanding form.

Had there been some technical or tactical shift that has enabled him to emerge, according to Wayne Rooney, as one of the best three central defenders in the world - and, by anyone's estimation, the best available to Roy Hodgson?

As Smalling sits in a leisure centre near Manchester United's training ground, he looks within for the answer. The first step was challenging himself to take more responsibility after the exodus of experienced defenders from Old Trafford when Rio Ferdinand, Nemanja Vidic and Patrice Evra all left in 2014. With over 1,000 United appearances between them, there was a big hole.

"When Louis (van Gaal) arrived, the centre-back position was very much up for grabs," he says.

"It was a question of, 'Who wants to take it? Who wants to fight hard enough to make it their own, to show that they belong?'

"I saw it as an opportunity to be that voice, that leader. I wanted to show the club didn't need to go and buy all the players they were being linked with, top centre-halves."

The chance was there but he needed to find consistency.

He worked on it with the help of a sports psychologist.

"For me, it was a case of focusing," he says. "You can have so many different demands; trying to please the fans, pleasing the manager, please yourself. You can put too much pressure on yourself.

"You can start forcing balls, maybe trying too hard. You make things too complicated. It's about uncluttering the mind."

The results can be seen in his new-found assurance, one of United's most dependable players along with goalkeeper David de Gea. He talks of making better decisions on the pitch.

"When I first joined United, I had ups and downs," he adds.

"As a centre-back, the manager doesn't want to see dips."

It is a reminder of Alex Ferguson's remark that he cannot stand emotional defenders. Strikers? They can be as temperamental as Eric Cantona. But the former United manager wanted centre-backs to have ice for blood.

"You can't be (extra) emotional as a defender, you can't overreact," Smalling concurs.

"You get punished if you do.

"With the sports psychologist, we do a lot of visualisation in terms of future games, what's coming up... so I am not too hyped."

He is reluctant to say who he sees and comes across as a softly-spoken man who seems to appreciate his good fortune.

When he was 18, he had little reason to think that he would become a professional footballer.

After a short, unsuccessful spell in Milwall's academy, league clubs had failed to see much in a lanky young defender who was athletic but not dominant on the ball.

He made the England schoolboys side but with A levels in business studies and economics from a school in Kent, he was thinking ahead to a business degree at Loughborough University.

Yet, football was his dream. In his last year at school, he sent out letters to clubs, alerting them to his forthcoming fixtures.

"I wrote to Gillingham, Charlton, London clubs and a few others," he says. "I explained my favourite position, my best traits and just said, 'Please come watch if you are interested'. I had nothing to lose."

He is not sure if the letter made a difference but eventually Fulham paid £10,000 (S$21,100).

He stayed at Craven Cottage for two seasons before United splashed out about £11 million in 2010, just beating Arsenal.

It has taken a while for him to become a regular. But he is on a run of 22 straight league starts, beating his previous best (eight in early 2011).

"I knew if I got that run of games, I could show everyone what a good player I am," he says.

He smiles at that quote from Rooney about him being one of the top three centre-backs in the world. Does he agree? "Well, it's nice to hear," he says. "Some people might roll their (eyes) but it spurs me on to fulfil those words."

His form is beyond debate.

United have the best defensive record - only 10 goals conceded in 15 matches.

He has helped keep nine clean sheets - no Premier League defender has more. And he has picked up just one yellow card despite playing every minute of every league tie.

Indeed, at 26, and playing with composure, perhaps a captain is emerging, although he would make an understated one rather than the Tony Adams style of warrior he admired in his youth.

He needs a few more years like this to join the honour roll of noted United centre-halves but Smalling hopes to be remembered one day like Gary Pallister and Jaap Stam, Ferdinand and Vidic. He learnt under the last two and likes to think he can combine their styles.

"Vida the rock, Rio so elegant," he says. "I learnt from both."

THE TIMES, LONDON