Less than a year ago, I woke up on the morning of the second Test between Australia and New Zealand in Hobart with the news that Viru had become only the second man to a double-hundred in ODIs.

My first thought was, "About time."

To me, Virender Sehwag has been the most exciting player I've watched, bar none. Yes, I know I belong to the generation that played against Viv, but having seen more of Viru than Viv, that's where I come from.

With Viru, you never know what's going to happen. Sometimes his batting doesn't work, sometimes it can be frustrating. When it works, though, he shakes up a game and turns it on its head. In Hobart that day, I thought that had Viru batted in ODI cricket the way he did in Tests, he could have got five double-hundreds. Or more.

But it is in Test cricket that Viru has shown us his genius. He has revolutionised Test batting, changed the way people look at openers, and made such an impact on the game that the rafters shake when he gets going.

Viru's 99 Tests, like his batting, seem to have gone by at top speed. A hundred Tests is a telling number, but then so are two triple-centuries, a strike rate of above 80 in Tests, 8400 Test runs, and the aforementioned double-hundred (off 149 balls).

It is always hard to judge a player in his first Test, but by the time Viru had played about a dozen, I did think that he had it in him to become something. For his first 30-odd Tests, I worked with Viru as his coach and it was a sheer delight to see him grow.

He came into the team in the guise of this middle-order batsman who had grown up on Indian wickets who could smash it everywhere. In about two years and a bit, he became a world-class Test opener with powers feared by all opposition. Over the rest of his career, he has become one of the greatest openers in the history of the game. People don't normally ever do that - go from being a middle-order batsman in India to opening in Test match cricket and producing outstanding performances all over the world.

What Viru was able to do was play tricks on cricket's very framework. If middle-order batsmen are asked to open the innings, they go into existential dilemmas, modify their game, work on technique. Many fail, a few cope. You will have heard all those stories.

Viru was different; he had no such crisis. He opened in Tests the way he had batted in the middle order - still smashing it. He didn't redefine his game because of his batting position. He redefined the position with his batting. I do not use the word genius casually.

I first met Viru in 2000, when he joined the squad to play the one-dayers against Zimbabwe, my first full series as coach of India. He looked a lovely kid - shy, with a mischievous smile, still innocent and wide-eyed, like many of the young Indians coming into the side.

Three months later, he made me sit up when he scored 58 against Australia in the Bangalore ODI. It was an innings of timing and confidence against bowlers like McGrath and Warne. We moved him into the opening slot in ODIs in a tri-series in Sri Lanka for two reasons: we had opening problems, and Viru kept getting out trying to slog the spinners in the middle overs. He nailed opening the batting beautifully - with it, he solved our problems and found he could play his game at its fullest. It should have been a different matter in Tests.

In Test matches he had a reasonable start as a No. 6, with a century on debut in South Africa and two fifties. We were struggling with Test openers and Sourav and I decided to gamble by sticking him in at the top of the order at Lord's, in only his sixth Test.

When we talked to him about the job, he didn't look like he was too worried about opening. He certainly didn't express it to me (and we had begun to speak very freely to each other by then). In his first innings as a Test opener, Viru was the team's top scorer, with 84. Then, when I saw him on a green wicket in Trent Bridge, in the second Test, I thought, "This guy is serious." He got a century and didn't look back.

Viru's coach in Delhi taught him to have a beautiful, straight backlift, so when he defends he is nicely straight and late. His attacking game wasn't too bad either. He could play so late and generate such bat speed that if you were a few inches off target on the off side, the ball was gone. Anything a bit straight was whipped through midwicket. He could also use the pace of the ball to score more effectively than most in the area between point and third man.

Early on, we widened his stance a little, and I used to encourage him to keep his head very still and not let it move sideways. When his head is perfectly still, like with any batsman, it allows him to play his late options and makes the most of his sublime balance. He is a great opener, though, because, along with everything else, he is fearless.

"One of the things that I think helped him find his feet in cricket and stay grounded was that he accepted his fate. If he nicked something, he accepted it and wouldn't worry about it"

Maybe he enjoys opening because he goes out to a clean slate. There are no wickets down, there's no responsibility like there would be coming in at six with four down. He goes in without any numbers and can do what he has said he does: see the ball, hit the ball. In a game filled with jargon and technique and dissection, it is like Viru knows why the great baseball catcher and manager Yogi Berra made total sense when he said: "How can you think and hit at the same time?"

Viru's instinct sweeps him away, and it is what makes him an attacking batsman. At a basic level, he must sense that instinct is swifter and more accurate than thought. Thought gets in the way. When batsmen are playing well, everyone goes by instinct, but Viru had that coupled with intrinsic fearlessness. It doesn't matter what the game situation is, who is bowling, what the wicket is doing. He sees the ball and he hits it - for four if he can.

As captain, batting partner or coach, it is best not to get in his way or try to complicate him. It would ruin Virender Sehwag. He is a natural in more ways than one.

He is one of the best balanced players I've seen. Plus, he catches like he is picking apples, and in those endless beep (fitness) tests we put the team through, he would turn on a dime. He was effortless at changing direction and caught everyone on the turn.

One of the other things that I think helped him find his feet in cricket and stay grounded was that he accepted his fate. If he nicked something, he accepted it and wouldn't worry about it. It was not that he didn't experience disappointment or didn't care, but he wasn't someone who beat himself up too much. What was over was over and he would start his next innings.

I don't know if that is what you call fatalism. Once, we flew into Melbourne in a storm and the plane was getting tossed around a little. He took one look at my face - I'm not the best of fliers - and started laughing. "What're you laughing at?" I asked him, and he said, "Relax, John, if the plane goes down, it goes down. There's nothing we can do about it." It didn't make me a better flier but it told me a little more about Viru.

The only thing that frustrated me, and that had me get stuck into him, was that for the team's sake, there were times when he needed to rein it in a little. But I knew that too much of that could ruin him. People talk about our little incident at The Oval, when I upbraided him. I made an example of Viru because I wanted the rest of the boys to understand that you have to adapt your play to the team's need to win the match.

We sorted that out later, and to his credit, he got over it and we remained mates. After we won the series in Pakistan in 2004, he insisted that I be part of the awards ceremony. I tended to avoid them because the limelight and celebration, I thought, belonged to the players. Viru had noticed this. After the victory he put his arm around my shoulder. "This time, John," he said, "you're coming with me", and dragged me down the stairs of the Rawalpindi dressing room to be with the team.

Viru is the only player I've watched who has pulled off a game suited for ODIs in Test cricket. If he had played ODIs like he played Test matches, he would have had much more success. In ODI cricket, I think he tries to up the tempo when he doesn't need to; he has already pushed the envelope as far as it can go.

Today he is 34, a senior player, a father, and not the cheeky kid I first met, though his smile still seems to contain its old mischief. I would love to believe that he has a lot of good cricket left in him, but all batsmen know that when they get to around 35, they have to work doubly hard on their fitness. It's not going to get easier but he can keep going for as long as he loves the game and trusts his instincts.

On his 100th Test, I would like to say to him: very well played Viru and thanks for the entertainment. Remember, though, that what we talked about still stands - that it's not enough to have big scores; the great ones are those who get the big scores consistently.