For the men chasing Roger Federer at this year’s Australian Open, there was hope in Melbourne yesterday evening, hope that the Swiss star might do what everyone else cannot: beat himself.

After coolly knocking off his first 11 sets of the tournament, the world no. 1 lapsed as he might have three or four years ago, before he had learned to manage his supreme and seemingly endless talents. In two sets, Federer committed 35 errors, allowing the dogged and consistent Tommy Haas to turn a blowout into nail-biter and Federer’s first real test. The top seed prevailed as Haas tired, 6-4, 6-0, 3-6, 4-6, 6-2, expressing relief that he had survived.

Haas, on the comeback trail from serious injuries and looking stronger with each match, might have given up long before he had a chance. He stuck with Federer in the first set, but played poorly in the second as Federer cracked forehand winners and gave Haas nary a chance to make an aggressive play. When Haas stepped up for a second serve at 2-2, 15-40, it seemed about time for the 27-year-old German to make his dinner reservations.

Then something inexplicable occurred. Federer missed a few shots on break points, Haas held, smashed a backhand winner to open the next game, and then watched as one of the greatest players in history slammed the easiest of overheads into the top of the net, bouncing it out of bounds.

One forehand error later, Haas had a break and reason to forge ahead. His tennis came to life – more sting on his groundstrokes, better angles on his volleys – and he played more patiently, essential against a man who is too quick and too complete to lose points after one or two shots. In the fourth set, Haas won over the crowd with a show of reflexes worthy of a lightweight boxing champion, flicking back six successive Federer volleys and ending the point with a diving volley of his own. A few points later, he broke for a 2-1 lead.

Federer’s errors continued unabated. The man with the most varied tennis skills on the planet showed he also has proficiency in an array of mistakes, be they backhands, forehands, volleys, shank shots, moon shots, or, as it happened, three more overheads. In the fourth set alone, Federer committed 21 errors in a span of 61 total points, meaning the top seed ended 31% of points with a miscue. In his previous three matches, Federer had made 47 errors in 471 points, a ratio of 10%.

This calculation is worth a closer look. In sets one, two, and five – the sets Federer won – his error ratio was 17%,16%, and 12%, all above, but much closer to, his remarkably consistent performance against three lesser opponents in the first three rounds. Federer’s overall numbers are skewed a bit by his match against Max Mirnyi, whose serve-and-volley game dictates short rallies, lots of passing shots, and few errors. But even discounting that match, anything approaching 18% or 20% is a frightening number. Haas outperformed Federer in this category in every set accept the second, finishing the night at 13% – better by 3% – than he had done in his three previous matches combined. In the fourth set, Haas made just six errors as Federer sputtered, a ratio of 9%.

Federer had not fared well in fifth sets of late, losing six of his last eight. Unfortunately for Haas, he cleaned up his game this time, making fewer errors (six, for a ratio of 12%), winning all 10 points on his first serve, and ripping more winners than he had at any time in the match, with 18 of his total 66.Applying the same formula, this means Federer ended 37% of the points with winners, none more important than the two backhands – one down the line and the other an abbreviated, opposite court flick off a Haas second serve – that gave him a break point in the fifth game. Haas missed his next forehand by less than an inch, and then Federer, seemingly within reach a few minutes earlier, was gone.

No matter the outcome, the tenor of this match offers some hope for the rest of the men’s field, especially David Nalbandian and Nicolas Kiefer, two men who have troubled Federer in the past and have the consistent, penetrating ground strokes that can keep him off the attack and give him time to make mistakes. For all his brilliance, Federer can be counted on for a cold spell or two. The only problem is he cannot be allowed to emerge from it. If he does, what seemed like an opportunity inevitably turns into a footnote to his latest championship.

Haas missed a rare chance last night. The next three men standing between Federer and a seventh major title may not be so lucky.

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Samantha Stosur may not have been able to put an end to Martina Hingis’s spectacular return to professional tennis, but she showed Kim Clijsters the way. Stosur, an Australian playing for her hometown fans, offered little resistance in the first set of her fourth-round match before reminding Hingis why it was so easy to walk away from tennis three years ago.

Stosur belted her groundstrokes throughout the second set, pinning Hingis behind the baseline and forcing her to hit short balls. She also clobbered Hingis’s weak serve, winning 23 of 50 points before falling 6-1, 7-6 (8).

Clijsters, who has been more likely to default than dominate in her first four matches, said her injured hip and back held up well in her 7-6 (5), 6-4 victory over the steady Francesca Schiavone. If Clijsters can move well and take full cuts, she should end Hingis’s run and move into the semifinals.

tperrotta@nysun.com