TENNIS/Australian Open: For about five or six minutes it appeared as if Fortress Agassi was about to be breached.

First a drop shot which the great man's skittering legs failed to reach, then an unforced back-hand error after a long rally. Paradorn Srichaphan was 2-0 up, and memories of his straight-sets second-round Wimbledon victory over the American, their only previous meeting, came flooding back.

Any slam defeat for Andre Agassi has been something of a shock since his second coming in the late 1990s, and that 2002 defeat to Srichaphan was one of the most startling. For a while there was cathedral quiet inside the Rod Laver Arena yesterday: was this to be the day the American's unbeaten run at the Australian Open, stretching back to the start of the millennium, and encompassing three titles, was to come to an abrupt end?

Then came another drop shot - cheeky and testing. All eyes were fixed on the Agassi legs, which blurred into fast-forward, accompanied by a burst of staccato grunts. This time he reached it, and the crisis suddenly eased.

It was not quite over, though, and before the opening set was won Agassi had to save five set points. But thereafter the Srichaphan challenge gently subsided, with Agassi winning 7-6, 6-3, 6-4 for his 25th consecutive victory in this tournament.

Next comes a repeat of last year's quarter-final against France's Sebastien Grosjean.

"It's like when Pete Sampras went on his big Wimbledon run. I think it's Andre's title until someone takes it away from him," said Andy Roddick, who surged into what promises to be a thrilling second week in the men's draw with another crushing victory, this time over Holland's Sjeng Schalken, who was beaten 6-1, 6-2, 6-3.

Roddick and Agassi are due to meet in the semi-finals, although Roddick has first to put away Russia's Marat Safin, who in his fourth-round match defeated James Blake 7-6, 6-3, 6-7, 6-3. Safin has the power to knock Roddick out of his stride, and the Russian is displaying a sense of purpose that should signal a return to the top 10.

Agassi has been a little disappointed that the weather has been considerably cooler here than usual. "I enjoy playing in the heat, although you are never sure when the weather is going to be your friend or come as a curse."

Agassi will be 34 in April and, despite being surrounded by young bloods, continues to defy them all at this tournament. If he does again, much will be down to his coach, Darren Cahill, formerly with Lleyton Hewitt.

"He's coached the youngest number one in the world and the oldest, and he constantly helps me improve by always being aware of the subtleties that make my game tick," said Agassi. "But it gets harder every year."

Many believe this may be Agassi's last year. Three years ago, when he won his third Australian Open, he gave what some thought was a valedictory speech. But back he came to win again. Second guessing Agassi has never been a fruitful occupation.