Have we seen Nadal's best?

So much about the Australian Open suggests a year of intrigue and fresh storylines, but there is disturbing familiarity to the biggest story: Rafael Nadal's fading invincibility, and the notion that we've seen the best of his rivalry with Roger Federer.

Nadal came to Australia without a tournament victory in eight months, along with a 1-9 record in recent matches against Top 10 players. Last year he was brought down by significant knee and abdominal injuries; now it's the right knee again, forcing him to retire in the third set of his Tuesday quarterfinal against Andy Murray, who was leading 6-3, 7-6 (2), 3-0.

For those looking forward to the semifinals, the overriding theme will be Murray's quickness, creativity and anticipation, each at a noticeably higher level in the wake of his rigid training regimen. This was the biggest match of his career, and he did not disappoint. "I'll be shocked if Murray doesn't win a Grand Slam tournament soon, and I'll be very surprised if he doesn't get three or four," former tour great Mats Wilander said the other day. "Right now it's against his nature to hit bigger shots, but he has to be more tactically aggressive and force the other guy to hit shots they don't want to hit. Andy's still young, but he's old in the head, so he can do it."

As for Nadal's mood going in, the Spaniard had admitted, "This match can change a lot the situation for me." It certainly does, although in truth, it reinforces an existing pattern. Nadal has been punishing his body for years, revealing himself as one of the most relentless competitors in the sport's history, but now comes the payback: physical breakdown. Never quite comfortable with the English language, Nadal tends to talk the way he plays: hurriedly and self-contained. He'll speak of coming back strong, and he'll work as hard as possible to get there. His opponent will be the forces of doubt.

• Andy Roddick burst onto the scene 10 years ago with such a violent service motion, people figured it was just a matter of time before his shoulder collapsed. He was the Ron Guidry of tennis, a slightly built guy generating incredible power from a skinny arm -- a rotator-cuff operation waiting to happen. Somehow, Roddick persevered. His style proved to be economical and extremely reliable (why so many women toss the ball to the moon, instead of copying Roddick's flick-and-blast technique, I'll never understand), and his serve has consistently been among the most feared in the game.

During the break between the first and second sets of his Tuesday quarterfinal against Marin Cilic, Roddick required a medical timeout for sore shoulder. He explained later that he couldn't pinpoint the injury, suggesting it was a nerve issue that left his arm and fingers numb, and that he was told he ran no risk in continuing to play. Still able to rip the ball with authority ("just not enough control"), he rebounded from a two-set deficit to square the match and temporarily put Cilic on his heels.

"He has just gone away," Mary Carillo said of Cilic on the ESPN2 telecast. "Andy's giving this guy a nervous breakdown." But Roddick couldn't sustain his aggressiveness through five sets and wound up going down rather quietly as Cilic, admirably steeling himself, dominated the final games.

We'll see in the coming weeks if Roddick's shoulder issued him a warning or whether it's a temporary malaise. Considering Nadal's plight, a back injury that removed former world No. 1 Dinara Safina from the women's draw, and assorted other ailments at the outset of the year, the sport is bound to hear more critics calling for an extended winter break.

• If you've stayed with the television coverage from Melbourne, you're likely predicting a Serena Williams-Justine Henin final -- a dream scenario for the sport. Serena is playing far too well to have problems with Victoria Azarenka, and after Venus Williams overpowers Li Na (the big Chinese breakthrough is coming, but not here), count on Serena to win the sisters' matchup in the semifinals.

Serena looked decidedly sluggish and overweight at the outset of recent Australian Opens, but arrived trim and prepared this time, an absolute force from the beginning. She's not just serving better than anyone in the tournament; I wonder if any woman in history ever served with Serena's combination of power and accuracy when she's really on form. She has an equipment edge over past greats, no question, but watching Serena's serve recalls the sight of Steffi Graf's forehand when she launched her domination of the sport: It's a level above the rest.

Several experts discounted Henin's title chances after her leg ailment became such an issue over the first two rounds, but she looked pretty spry in her straight-set victory over Nadia Petrova. As well as Zheng Jie played against a sore-hipped Maria Kirilenko, she's not in Henin's class on this brand of stage, no matter how long Justine was away from the game.

"She's just such a good player and fighter," Serena said of Henin. "I think she brings a totally different theme to the game." Elena Dementieva got a long look at Henin's arsenal in the second round and said, "It just doesn't feel like she had the break (from tennis)." Henin has been unabashedly thrilled with it all, saying, "It's magical out there, the way I feel. I feel so happy on the court. I feel it's my place."

Stirring moment from the first set of Henin's fourth-rounder: With Yanina Wickmayer up 6-5 and 15-40 on Henin's serve, Henin uncorked an all-out, down-the-line backhand winner that landed almost squarely on the corner for a winner. That was the first of three set points she survived, thanks to an attitude she calls "staying calm, but being brave."

• Not that it really made a dent on a bleak landscape for American men's tennis, but Donald Young made a positive impression, particularly with the forehand, in his second-round loss to Lleyton Hewitt. The turning point: With Hewitt serving at 5-6 in the first set, Young got to set point on a second serve at 30-40. Staying back, approaching the moment far too tentatively, he hit a looping forehand return that Hewitt answered with a strong crosscourt forehand, and Young netted his down-the-line backhand. The set drifted away from him, and Hewitt won it in straights.

An equally upsetting episode, in its own way, for Young: During his first-round match against Cristophe Rochus, a ballboy really had to pee and couldn't hold it back, thoroughly wetting his pants right there on the court. The incident forced a long delay, complete with sawdust and a blower, and the 20-year-old Young -- forever trying to achieve his long-heralded potential -- had to be wondering, "Why does this happen in my match?"

• NOTES: For months after Serena's meltdown at the U.S. Open, the name of the foot-fault-calling lineswoman was a mystery. It finally came to light in Australia as reports noted that Shino Tsurubuchi, a Japanese national, worked the recent Brisbane tournament and then moved on to the Australian. She hasn't worked any of Serena's matches so far, and that's not likely to change . . . Interesting that James Blake glared at Juan Martin del Potro after some of his Argentinian supporters got a bit too vocal during their second-round match. Blake's fans at the U.S. Open, a very loud and conspicuous group of longtime friends known as J-Block, have been known to irritate an opponent or two . . . You wonder if Maria Sharapova has heard what Phil Jackson, the Los Angeles Lakers' coach, said about her boyfriend, Sasha Vujacic, before the NBA season: "He's just an emotional player that plays by the seat of his pants, and that's about it. He doesn't have a brain." Perhaps, but he's the envy of many young men just now . . . During their playing days, I would have traveled great distances to watch Patrick Rafter or Henri Leconte play tennis. They entered the Legends Doubles together in Melbourne, undoubtedly a treat for seasoned fans . . . Cilic is the latest in a line of towering, highly competent players from Croatia. Think of it: the 6-4 Goran Ivanisevic, the 6-5 Mario Ancic, the 6-10 Ivo Karlovic and the 6-5 Cilic. And none of them, by all accounts, has a mean-spirited bone in his body . . . Often brutally honest, Roger Federer described his lifetime edge over Hewitt as "more raw talent." Sums it up pretty well, doesn't it? Federer did credit Hewitt, though, for helping him get "mentally tougher" over the years . . . Pretty racy move by Venus, wearing skin-colored underwear that create the "illusion," as she says, of wearing nothing at all . . . Nice to hear some of the Melbourne fans jeering Azarenka and imitating her constant, annoying shrieks. Azarenka needs to hear that, because it's an awful noise that makes her matches extremely difficult to watch -- especially on television, where courtside mikes amplify every sound . . . Tell me Nikolay Davydenko isn't going to beat Federer in the quarters? Davydenko may have been refreshingly charming in his press conferences. He may own recent victories over Federer and Nadal. He may be "the best tennis player on the planet for the past three months," as the esteemed Richard Evans wrote on FoxSports.com. But compared to Federer -- and most players -- he's an aesthetic disaster on the court. Send him away, Roger, if you don't mind.