MELBOURNE, Australia — On paper, Serena Williams’s 6–2, 6–1 first-round victory over Mara Santangelo, the no. 27 seed at this year’s Australian Open, looks convincing. Don’t be fooled by the score.

On a cool, clear Monday evening in Melbourne, hours before intense heat was scheduled to arrive, Williams advanced to the second round, thanks to a heap of errors (23 in all, including four double faults) and a lousy strategy from her opponent (in brief, trying to hit winners rather than making Williams run). Santangelo, a wiry Italian who hits with so little spin that one can routinely spot the black lettering on the ball as it zips by, makes a compelling case for a return to the days when Grand Slam tournaments seeded 16 players rather than 32. Santangelo has earned her ranking, but a player of her caliber doesn’t deserve any protection from the top women in the draw (a seed can’t play another seed in round one). If she’s randomly selected to play Maria Sharapova in the first round, so be it.

But we digress from our chief topic: the very sad physical condition of one Serena Williams and her denial of this fact. In the press guide of the WTA Tour, Williams is listed at 5-foot-9 and 135 pounds. She’s at least 20 pounds heavier than that, probably more. It was clear early on last night that Williams had no ability to retrieve sharp angles and could barely hit groundstrokes on the run. Her footwork is suspect, and although she claimed to have served well, she only made 47% of her first serves (she did have 10 aces). If Santangelo had decided to do something other than slap the ball around and take risks on every shot, this would have shaped up to be a much different match.

More frustrating than Williams’s poor conditioning is that she wants us to believe that she’s been working hard. She said she skipped last year’s fall season, after the U.S. Open, because she had to tend to a legal matter (a civil lawsuit involving her father and a “Battle of the Sexes” tournament). She reasoned that she would train instead, and by the look of things, many of these workouts involved a remote control and a 50-inch plasma screen. Unless you take Williams at her word: “Fitness is fine,” she said after her victory. There was more: “I can definitely win a third title, for sure,” she said. “My mom and dad always taught me to think positive. For me to sit here and say no now, I just can’t do that. Now whether I win, lose, or draw, that’s, you know, up to me.”

Williams used to have control over wins and losses, but not these days. She might well win two or even three more rounds this tournament, considering her draw. If she somehow does win the title — with the aid of, say, a fast-spreading and debilitating disease in the women’s locker room — it would be an indictment of the rest of the draw, not a credit to Williams. Nothing can change the fact that she remains less than half the player she once was back when she could scramble, charge the net, and hit fabulous winners from a full stretch. No one played quite like her before, and no one has since, but she doesn’t want to be that player anymore. She’s obviously not concerned about her surgically repaired knee, either, or she wouldn’t subject it to the strains of competition while she’s in such poor shape. There’s no reason to stop watching Williams; even at her worst, she’s better than most and often very entertaining. But if you haven’t stopped listening to her by now, the time has come.

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After being put on the endangered species list at Wimbledon last year, a surprising mammal is thriving at the Australian Open this year: the American male tennis player. Everyone expected Andy Roddick and James Blake to have solid tournaments, but Zack Fleishman, Mardy Fish, and Sam Querrey?

All those men and more remain alive and well. Fleishman, a 26-year-old from Santa Monica, Calif., won his first Grand Slam match on Monday over Agustin Calleri. He had to qualify for the tournament and is ranked no. 170 in the world. Querrey, a 6-foot-6-inch 19-year-old, also won his first Grand Slam match, defeating the far more experienced Jose Acasuso, seeded no. 27, in four convincing sets (the 16-seed limit should apply to the men, too). Querrey recently worked out with Roddick for a week in Hawaii, where he said he defeated his tutor for the first time in about 20 tries. Querrey said Roddick, who downed Roger Federer in an exhibition match last week, joked about the loss upon arriving in Melbourne. “I saw him in the hotel lobby and he said, ‘I can’t beat you in a practice match but I can beat Federer.'”

While Fleishman and Querrey posted nice wins, Fish outdid them both by bouncing the no. 4 seed Ivan Ljubicic, who is in no danger of losing his reputation for failing miserably in the tournaments that count the most. The Croat, who won a warm-up event in Doha this month, has only survived the third round of a major tournament two times in 30 tries. For a player of his ability and rank, it’s a pitiful distinction.

Fish, however, deserves the credit, rather than Ljubicic the blame. The 25-year-old American has slowly worked his way back inside the top 50 after two surgeries on his wrist in 2005. Fish has done more than recover from injury. With the help of his coach, former American standout Todd Martin, he has remade his suspect forehand, changing his grip and lowering his backswing. “I was lost,” Fish said. “I had no confidence whatsoever, and I needed to do something.” Now that Ljubicic is gone and Fish is found, the American could easily find himself in the fourth round. Several other American qualifiers, including Alex Kuznetsov, a talented 19-year-old, take to the courts today.

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SHARAPOVA NEARLY UPSET In early action today, Sharapova, the top seed, struggled through injury and 100 degree heat to defeat Camille Pin, ranked no. 62 in the world, 6-3, 4-6, 9-7, in two hours and 51 minutes.

The tiny Pin scampered around the court and forced the 19-year-old Russian into 65 errors. Sharapova squandered a 5-0 lead in the third set, showing her frustration when the chair umpire ordered a point to be replayed after a ball fell out of Pin’s skirt. “Are you f——kidding me?” she said. She took an injury timeout after gaining a 6-5 lead, when she seemed to be suffering from sharp pains in her lower abdomen. Pin took the lead 7-6, but double faulted on break point and proceeded to collapse.

tperrotta@nysun.com