Throughout this long and cold January Chelsea's training ground in Harlington has been a raw and barren place. Whenever the wind and rain whip across the exposed fields it seems as if yet more bracing questions are being asked of Gianluca Vialli and his lavish and culturally disparate squad.

During such icy moments, Vialli looks exactly like a 34-year-old man who has been a football manager for almost a year. Even when the early morning banter kicks in, Vialli often appears preoccupied, almost brooding on the exacting expectations that now surround his team.

It is possible to imagine Vialli instructing himself that, above all else, Chelsea need to retain the resilience and defensive solidity which have become the club's trademarks since he replaced Ruud Gullit as player-manager last February.

There are various reasons for Vialli's astonishing success over the last 11 months, ranging from his practical maintenance of the best features of Gullit's tenure to his measured but astute use of Chelsea's wealth while signing Marcel Desailly and Albert Ferrer to strengthen his defence. Yet perhaps Vialli's greatest attribute is his capacity to combine a reassuring warmth towards his players with a more searing passion to avoid defeat.

Vialli's generosity is often heard in his answers. "I don't want to seem humble," he suggested a few Fridays ago, just before Chelsea extended their unbeaten run in the league to 21, "but I think it's down to the players. They have a great desire and a point to prove because Chelsea have always been known as a team who can play very nice football but who are also quite inconsistent.

"I have a few ideas about the way we should play, but it's the players who make it happen."

Vialli realises that most footballers respond best to such magnanimous praise but, up close, it is clear that his ease with others is a gift rather than a trick. Whether he is laughing as Gianfranco Zola leaps to slap his hand in a high-five or cuddling the old boy who brings over the practice bibs, Vialli transcends the gruff bluster so many managers use to convey a sense of authority.

Like all football teams Chelsea engage in a series of mildly absurd games which, apart from deepening their unity, are primarily revivals of heightened adolescence. A typical encounter sees the squad divided into two rows of 10. Graham Rix, Vialli's assistant, stands eight feet between them. He waves a yellow bib as a sign for a member from each side to sprint towards him. When one player touches the flapping marker he races back in the hope of reaching his own line before being tagged by his opposite number.

It is as banal as that, and yet, for the Chelsea millionaires lost in the heat of every noisy chase, the celebration of each victorious runner is an exaggerated exercise in delirium. Whenever Vialli wins, his reaction is unchanging. Back as a boisterous member of the Chelsea crew, he spreads his arms wide and wheels away with a look of rapture as intense as if he has just scored a European Cup final winner.

The similarly ardent motivation Chelsea called upon during their recent 1-0 defeat of Newcastle was the most obvious example that, even though Gullit insisted that Vialli's Blues were "my team, my system, my vision", the players themselves know that their spirit stems from the current manager. But for Vialli, instead, "they finally realised that we have to be solid.

"Arsenal won the Premiership last season because they were the most solid team in the land. They conceded very few goals. I think it depends on the way the whole team approaches the game. Our two strikers must be the first defenders when the opposition have the ball. If other teams want to score they must know they have to get past all 11 players. It's a simple philosophy."

It is also the kind of stuff which, in a deep and sombre voice, Vialli churns out effortlessly when meeting the media every Friday at noon, an exercise he so masters that Chelsea are able refuse all requests for individual interviews.

"As a manager," he said earlier this month, "you have to sow a seed of imagination in your players. Of course you give them an idea of the way you want them to play tactically, but if you insist too much, they can lose their imagination. I don't want robots."

While fun has been had after Vialli's occasional linguistic slip, particularly his pledge to keep Chelsea fighting when "the fish are down", his English is often as considered as it is expressive. Before the Gullit showdown, as the tabloids searched for a big headline dripping with revenge, Vialli avoided every verbal trap.

Even near the end, when a persistent hack asked him why he had not written personally to Gullit to congratulate him on his Newcastle appointment, Vialli remarked wryly that his good wishes had been verbally conveyed through the newspapers themselves - because, he said, the tabloids deliver a message "more quickly and safely" than the post office. When I asked him a week later if he ever wished he could swap such managerial chores for the simple pleasure of only playing football, Vialli did not hesitate. While he loved playing, he regarded himself as a manager. It was a description, and a vocation, in which he could revel.

"I hope I am a much better manager now than when I started," Vialli said. "Management is about improving your relationship with the players and the journalists, about learning to read a game better so that you can make changes. I hope I keep improving as a manager for the rest of my career."

Vialli's next big test comes tomorrow when Chelsea are away to London's other championship contenders, Arsenal.

Two weeks ago Chelsea struggled at home to Coventry, the last team to beat them in the league on the season's opening day. After they had fallen behind in the seventh minute Chelsea salvaged Europe's longest current unbeaten league run, and their slot at the top of the Premiership, with brilliant individual goals at the end of either half. It was, once more, the kind of desperate win every championship team needs.

After both goals Vialli turned and walked resolutely away on his own. He knew where he belonged. He was a manager and, almost a year on, his work had only just begun.