Djokovic fights through fatigue to triumph in five-set thriller

As Roger Federer sits atop the rankings, lord and master of all he surveys, his world looks blissfully serene. The great man has barely broken sweat easing into the third round (it might spoil the look of his all-black evening outfit designed specifically for night sessions) but this is the calm before the storm. The game's future is flexing its muscles here and Novak Djokovic and Andy Murray are making a case for a tilt at the top, sooner rather than later.

Djokovic has already positioned himself on the heels of Federer and Rafael Nadal, rising through the ranks this season and establishing himself as the third best player in the world. And while his talents and power are obvious to see, it is the warrior in him that is beginning to worry the boys at the top.

He came through the match of the tournament so far, surviving a four hour 44 minutes onslaught from Radek Stepanek to reach the third round 6-7, 7-6, 5-7, 7-5, 7-6. Once it was over, both men were exhausted and both were happy to heap praise on the other. As they embraced at the end, Stepanek pretended to collapse into the Serb's arms, much to the amazement and eventual amusement of his rival. Stepanek is not normally known as much of a joker.

Stepanek had tried everything he knew to worry the third seed and, as a former member of the world's top 10, he does know a trick or two. Only a back injury last summer caused him to fall to his current position of No 35 in the rankings but now that he is fit again, he is willing to run for days in pursuit of victory. But nothing Stepanek did seemed to dent Djokovic's confidence or belief that only he belonged in the next round.

Since he broke into the top 10 at the Indian Wells tournament in March, Djokovic has had his eyes on the top of the heap. By winning the Masters Series title in Miami, he knew that he was standing on the tails of Federer and Nadal, and by beating Federer to win the Masters Series title in Montreal, he showed that he was ready to knock the big boys from their perches. Quite what he has left in the tank after yesterday's marathon is anyone's guess.

He needed treatment to his back – a regular problem when he gets tired – and his legs. "I was cramping a bit in both legs, in my arms, in my back," he said. "I was cramping a bit in my head, too." The pain did not matter, though, provided he got the result.

He now plays Juan Martin Del Potro, the 6ft 5in Argentine who is tipped as the youngest of the young guns to challenge Djokovic and Murray when they get to the top. Del Potro started the year ranked 92 and is now up to No 57 – and he would be higher if it were not for his unfortunate habit of bumping into the top men in the early stages of major tournaments. He lost to Nadal in the first round of the French Open and Federer in the second round of Wimbledon. He might just have better luck against a tired Djokovic here.

All the while that Djokovic has been surging up the rankings, Murray, his old mate from junior days, has been watching wistfully from the sidelines. His run of injuries has knocked him back from being shoulder to shoulder with the Serb in March to staring up at him from 16 rungs below on the rankings ladder. Not that Murray is jealous or frustrated by his old sparring partner's success, adopting the philosophy that you deserve all you get in this game and Djokovic deserves to be near the top.

Murray's chances of closing the gap on Djokovic appear to be getting better by the day. He will play Hyung-Taik Lee today for a place in the fourth round. "I played him in San Jose this year," Murray said. "I won 7-6 in the third. He's a really good player. Very consistent. Solid. Does everything well. Doesn't do anything unbelievable, but he's in really good shape. He's got a good serve. Forehand, backhand is good. It's going to be a hard match. Lee can give anybody problems."

Should Murray come through that encounter unscathed, his route through the draw does not look easy, but it does look possible.

He is scheduled to meet Nikolay Davydenko in the fourth round and James Blake in the quarter finals. Provided Murray remains injury-free and provided he does not run out of steam, anything is possible here.