Novak Djokovic steel grinds Andy Murray down

There must be a few sports psychologists out there who would like to put Novak Djokovic through a CAT scanner. What happens in the world No1's brain when he is under threat on the tennis court?

Whatever it is, you can bet that every other athlete in the world would love to know. Wednesday's match here reminded us how difficult it is to bring this man down. In his seventh meeting with Djokovic this year, Andy Murray opened up with a set of near-perfect tennis, a set in which he dropped just three points on his own serve and hammered his forehand as confidently and rhythmically as a man driving a stake into the ground.

What did Djokovic do? He breathed deeply. He bided his time. And then he began turning up the pressure, little by little. Murray might have beaten him in two of their most significant matches this year — the US Open final and the semi-final of the Olympics — but that does not mean he has established any kind of ascendancy in their 14-year rivalry.

After Djokovic's 4-6, 6-3, 7-5 victory, Murray is trailing seven wins to 10 overall, and by four to three this year. The good news is that, if you are going to lose to Djokovic, this is the time. Murray came into the match with one win under his belt, and the round-robin format means that he still has a better-than-even chance of reaching the knock-out phase. The bad news is that, by losing top spot in Group A, Murray is likely to meet Roger Federer in the semi-finals. And that is the draw nobody wants. Federer is aiming for his third successive title at the Barclays ATP World Tour Finals and saw off Janko Tipsarevic on Tuesday with the dismissive air of a man telling his butler to stand down for the night.

Murray was equally commanding over the first 45 minutes yesterday. "I don't think I played badly in the first set," said Djokovic. "It was him playing really well, serving extremely well. I just had to stay mentally tough and believe that I can get my opportunities, and when they're presented to try to step in and use them."

This was a 21/2-hour match decided by impossibly small margins, so small that Murray attributed the result to the final two minutes. But the momentum began to switch when Murray had a break point early in the second set. Djokovic came in behind his serve and hit a drive-volley bang on the junction of two lines, right on the corner of the court. He surely did not mean to cut it quite so close, but it made for an unreturnable shot.

Was it jammy? Frankly, yes. But then Djokovic's X-factor is his ability to play with a loose elbow, as if just knocking the ball around in his back garden, when there are millions watching on TV. His ability to hit the lines at the big moments is uncanny. "I try to follow my instincts," he said, "and play the shots that I feel are right at that moment." If boxing is often used as an analogy for tennis, then that punchy drive-volley clearly hurt Murray. It shook his composure, and presaged a dip in his accuracy for the remainder of the second set.

There was plenty of shouty swearing too, just in case anyone imagined that his US Open breakthrough would eliminate tantrums from his game. For all the technical and temperamental improvements this season, he could still learn much from Djokovic's extraordinary ability to absorb pressure. "The intensity of my matches with Novak have been extremely high this year," Murray said. "I think both of us have seen things in each other's games improve. That's why there's a lot of long rallies, and the matches are incredibly tight."

One topic that provoked much discussion on the social networking sites yesterday was Murray's Adidas kit: he started with a black-and-gold T-shirt, twinned with bright yellow shorts. Then, after the first set, he changed to a white shirt, prompting a wave of online debate. Someone tweeted his mother Judy to suggest that he resembled a banana, though you could also make a case for an upturned milk bottle. Full cream, obviously.

Later, Jonny Marray was involved in an equally close call in the doubles. Playing alongside Freddie Nielsen of Denmark, Sheffield's Marray helped to close out the narrowest of victories against the world No?2 pair Daniel Nestor and Max Mirnyi. The score of 7-6, 4-6, 12-10 means that Marray and Nielsen are the first players in either singles or doubles to qualify for Sunday's semi-finals. The capacity crowd of 17,800 were whole-heartedly involved throughout both matches and London can now look forward to hosting this tournament for another three years, after a new contract yesterday extended the O2's tenure to at least 2015.