MELBOURNE -- Suddenly the fuzzy yellow ball seemed as big as the moon. It hung perfectly at his right shoulder, and Marat Safin swatted it and felt as if he were walking on the witnessing moon over the arena -- weightless though weary. Up high again, one thought on his mind: "I'm back."

With that one last surge toward the net and a crushing volley, Safin gave himself "the best birthday present of my life," a victory over Andy Roddick in five tingling sets last night, and a place in the semifinals of the Australian Open.

His 24th birthday was just about over when Safin emerged from the wilderness of a brilliant career that had come apart through carelessness and injuries. Remember, he was the 20-year-old Muscovite who made Pete Sampras look like a flattened sparring partner in the title bout of the 2000 US Open. A quick, powerful young man of 6 feet 4 inches with talent to burn. And he burned it noticeably here on his 22d birthday, playboying his way out of the final against a lesser foe, Tom Johansson.

He was the Headless Horseman of tennis, galloping in the wrong directions after barely missing No. 1 status for 2000, bumbling and tumbling, arriving in Melbourne at No. 86.

But from the genuine wilderness, a tent in Yosemite, he bounded back into the picture. Knocking the No. 1 ranking off Roddick's head, 2-6, 6-3, 7-5, 6-7 (0-7), 6-4, Safin found himself -- for one night, anyway -- king of the Peppermint Palace, the soft green-tinted Rod Laver Arena where a full-house crowd of 14,623 serenaded his triumph with "Happy Birthday to You."

"That was really nice," said Safin. "I can't ask for anything else. Especially the win, beating No. 1 in the world, playing the best since I helped Russia win the Davis Cup at the end of 2002."

He was able to play only 23 matches last year (12-11) because of damaged ligaments and nerves in his left wrist.

"I saw so many doctors and nobody could tell me what was wrong, what to do," said Safin. "They had doubts, they had versions. Finally, friends took me to a good sports doctor in LA who said it would heal in a cast. It took a month and a half. I had nothing to do. I was a little depressed. So I went camping. Me and my coach and his girlfriend.

"We went to Yosemite. It was great, beautiful. We went fishing, drink beer, cook what we catch. Just make your mind a little bit relax. Chill out. Think a little bit. No people. You need these kind of things." So nature boy, who won his first of 11 titles in Boston, the 1999 US Pro, decided to make a fresh start.

"I'm really surprised to be here [in the semifinals] because with so much time off you lose completely the game," he said. "You don't see anymore. You don't feel the moment, what to do, all these things. Basically you have to start from zero. But I did a great job, working hard, day by day, to make everything come back."

His labors continued in the tournament, punching the time clock as well as his volleys more than anyone else: two in five sets, three in four sets, a total of 15 hours 6 minutes on court. By comparison, Roddick spent 9:13.

"But it was really nice to play long matches," said Safin, "to feel the pace of the ball, to read where it's going, a little bit of feeling of the points."

His reward is a shot at the champion, Andre Agassi, who breezed in a 6-2, 2-0 TKO of Sebastien Grosjean, his 26th successive match win in this Open. The Frenchman quit early, citing painfully pulled thigh muscles.

When Safin summoned a trainer after the first game of the second set, trailing, 6-2, 1-0, customers groaned and wondered whether he, too, was calling it an abbreviated day. "I pulled something a little bit in my legs," he said. "I took some painkillers, that's it."

Safin would be the pain that killed Roddick's residency at No. 1 dating to his US Open triumph.

"Obviously, it's a nice number to have," said Roddick. "But I have 11 months to try to get it back. It's going to be jumping around this year. That's what makes it exciting. But Marat played great. I was happy that it was a good match."

A superb clash it was, heating a cool evening, both reaching for the jugular nonstop over a 3:23 stretch. During a shotmaking smorgasbord, the incredible was commonplace. Their go-for-broke rallies kept onlookers wailing. Although Safin probably would have been a tight end if he'd grown up American, his swiftness matched Roddick's as they stole points from each other with extraordinary saves.

"I thought I was lucky to win the fourth set," said Roddick. "But when I did, I thought back to last year, entering a fifth set against Younes El Aynaoui. Same night, same round, quarterfinal. I thought, `Is it going to happen again?' "

That five-hour wowser went to Roddick, 21-19 to finish.

Safin, blitzed in the tie-breaker, says he "rushed too much." But he wasn't in a hurry between points in the fifth. "You've been running three hours, and every point is important," he said. "You've got to take time, think a little, slow it down."

With steaming aces and winners flying from their rackets, the distance between them was narrow. Safin ducked a break point to 2-2 in the fifth with a service winner. He got the break to 5-4 with an angled forehand inside-out return, and a scooped low forehand that Roddick couldn't volley.

Roddick wasn't through. Blazing forehands earned him two break points at 15-40. "I felt I had my feet back in," he said.

"Right there it could go to Roddick or me," Safin said. He launched his 19th ace, at 120 miles per hour. One more chance. Roddick whanged a forehand that looked a winner -- until the tape intervened.

"I had to create, make things happen, not be passive," Safin said. He swooped in with his serve for a volley to match point, then dashed behind a forehand, forcing Roddick's last shot to rise to him like the moon. He shot the moon with a concussive, conclusive volley.

How will he prepare for Agassi?

"Some beers to relax my muscles, and a lot of sleep," he said.

Perhaps dreaming of tennis balls looking as big as the moon.