Federer puts positive spin on laboured progress but cracks show

He is on the verge of reaching his 18th Grand Slam semi-final in succession, but the evidence was clear: Roger Federer is not what he was. While a five-set victory over Igor Andreev kept alive the defending champion's hopes of winning a fifth successive US Open title here, it was not the display of a player we have come to regard as one of the greatest of all time.

Federer, who now meets the qualifier Gilles Müller in the quarter-finals, won 6-7, 7-6, 6-3, 3-6, 6-3, but the best you could say was that it was a performance showing his strength of character. Until the closing stages the world No 2's form was so erratic and his game so littered with errors that you would not have reckoned against Andreev, a 25-year-old clay-court specialist ranked No 23 in the world, pulling off the biggest win of his career.

If the match bore comparisons with Federer's five-set victory over Janko Tipsarevic at this year's Australian Open, it should be remembered that the Swiss, unbeknown to himself, was in the throes of glandular fever at the time. The suspicion remains that he is still living with the consequences of that illness, either in terms of the physical effect it has had on him or the disruption that it has made to a season in which the Olympic Games have added to the burden of an already demanding schedule.

"I feel I'm over it, but maybe I'm not playing my best yet, who knows?" Federer said. "I need to play my best, to get through the matches. Hopefully the best will come at the end of the tournament. That's what I'm looking forward to. I have no complaints. I don't feel I'm extra tired. I'm not scared of being super tired tomorrow. I don't think physically it was that much of a problem. Those are all good signs to have right now."

Federer is the eternal optimist. After almost every one of his 12 defeats to Rafael Nadal, his successor as world No 1, he has talked of the lessons learned and his confidence in doing better next time. Even here he put a positive spin on his performance against an opponent who won the last of his three titles three years ago.

"Being part of some dogfights is fun for me," Federer said. "I was really happy because in five sets you go through different stages of feelings, of playing well, playing badly. In the fifth set you try not to make that many errors, and hopefully get off to a good start. That's exactly what happened. I was just really pleased with my fighting spirit."

He added: "It's just fun to play on centre court. You practise hard in order to play when it comes to crunch time. I'm happy with the way I played today when the pressure was the highest and the crowd were going a little bit crazy. I think I'm at a stage where I'm enjoying playing much more again. For a while it was always the same for me – going on court and winning all the time – so maybe I don't take it for granted any more."

Federer had not lost a set in the first three rounds but looked shaky from the start here on Tuesday night. Two successive errors handed Andreev the first tie-break and the Russian threatened to go two sets clear before Federer found his touch in the second. Even after taking the third set the Swiss did not convince. Andreev, serving well and going for his shots on his forehand, levelled the match, only for Federer to make the decisive break early in the final set.

Müller, the world No 130 and the first player from Luxembourg to go this far in a Grand Slam tournament, earned his meeting with Federer by beating the No 5 seed Nikolay Davydenko, a semi-finalist in 2006 and 2007, 6-4, 4-6, 6-3, 7-6.

Federer or Müller will then play the winner of the heavyweight quarter-final showdown between Andy Roddick and Novak Djokovic, who won their fourth-round matches in contrasting styles. Roddick lost only nine out of 62 points on his serve in crushing Fernando Gonzalez 6-2, 6-4, 6-1, while Djokovic, who lost to Federer in last year's final, took three and a half hours to beat Tommy Robredo 4-6, 6-2, 6-3, 5-7, 6-3.

Djokovic complained of exhaustion and hip and ankle problems, though Robredo was less than impressed. "I have pain as well," the Spaniard said. "I was running like hell and my feet were burning, but I said nothing. I think that if you're not fit enough, don't play. But every time after he asked for a trainer he was running like hell and making the shot. But he does what he does a lot of times."

When Roddick was asked about which ankle Djokovic had injured he replied: "Isn't it both of them? And a back and a hip? And a cramp, bird flu, anthrax, SARS, a common cough and cold." Did he think Djokovic was bluffing? "No, if it's there, it's there. There's just a lot. He's either quick to call a trainer or he's the most courageous guy of all time."

Jelena Jankovic, the women's No 2 seed, continued her improvement with a convincing 6-1, 6-4 victory over Sybille Bammer to earn a semi-final against Elena Dementieva. "I feel that every day I'm better and better," Jankovic said. "I'm moving a lot better. At the beginning of the tournament I wasn't really feeling that great, because I wasn't able to practise. I was injured at the Olympics and throughout most of the year."