Jelena Jankovic became the latest big name to crash out of Wimbledon after slumping to a straight-sets defeat to Tamarine Tanasugarn.
The number two seed was simply not at the races on Court 18, losing 6-3 6-2 to the veteran world number 60, who finally reached the quarter-finals after six previous fourth-round exits.
Tanasugarn could hardly have wished for an easier passage against a truly out-of-sorts Jankovic, who delivered an error-strewn display to all-but gift her opponent victory.
Jankovic had survived a major scare against Denmark's Caroline Wozniacki in round three, when she overcame an early knee injury to triumph in three sets.
The Serb arrived on court sporting a partial bandage on her left knee but she appeared to be moving well early on.
Neither player shone in the opening five games, the pair both holding serve comfortably thanks to a high error count.
The decisive moment in the set arrived after Jankovic disputed a line call when she thought she had hit a backhand winner in game six.
From 30-30, she fell break-point down and despite saving two of them, another backhand error set up a third, which Tanasugarn accepted with relish.
Leading 4-2, the Thai simply waited for the Jankovic mistakes and comfortably served out the set.
Venus the victor at SW19
Defending champion Venus Williams breezed back into the quarter-finals with a 6-3 6-4 victory over Russian 18-year-old Alisa Kleybanova on Court Two.
Williams set about her task with brisk efficiency and her world-ranked 42 opponent seldom showed signs of rising to the occasion as she struggled to maintain parity with her opponent's searing ground-strokes.
Kleybanova, at 18 the youngest player left in the women's draw, fought out the early portion of the first set unscathed before a catastrophic service game with three double faults and a spooned backhand saw her broken for 5-3.
Williams duly served out to take the first set and from that moment the result was never in doubt. In front of a half-full and often only half-interested grandstand, Williams duly broke twice for a 4-0 lead in the second set.
Despite the air of gnawing certainty, Kleybanova bravely rallied, not only breaking Williams back once when she served for the match for the first time, but fashioning three points for an improbable double-break back.
Williams, however, held her nerve, pulling herself out of her hole and taking advantage of her second match point, a backhand stop volley at the net finally sending her back into the quarter-finals.
Serena breezes into next round.
Serena Williams followed sister Venus into the Wimbledon quarter-finals today with a routine 6-3 6-3 victory over fellow American Bethanie Mattek on Court Two.
Williams was simply too strong for Mattek, the world number 69, who was making her third-round debut, breaking in the first game of the match and maintaining her comfortable advantage throughout.
Mattek, better known on the tour for her bizarre fashion statements than her Grand Slam-winning credentials, turned out in a plain white dress and failed to add the required colour to her game.
Breaking for a second time to claim the first set, Williams pressed home her advantage by breaking again in the first game of the second set, and holding with ease to head back into the last eight.
Zheng Jie continues fairytale run
Zheng Jie reached her first Grand Slam quarter-final as the Chinese wildcard's Wimbledon fairytale continued with a convincing 6-3, 6-4 victory over Hungarian 15th seed Agnes Szavay on Monday.
Zheng had stunned top seed Ana Ivanovic in the last round and the world number 133 showed that was no fluke by demolishing Szavay in an hour and 21 minutes in the fourth round.
The 24-year-old doubles specialist is only the second Chinese player to reach the last eight at Wimbledon, matching Li Na's achievement in 2006.
Zheng plays Czech 18th seed Nicole Vaidisova for a place in the semi-finals after the most complete performance of her career.
'It feels great. This was a tough match. I didn't know how I could get to the quarter-finals because every opponent was very strong,' she said.
'But I feel I just played so well. I just gave her the forehand more because her backhand is unbelievably good.
'For me, today is the best tennis I've played. I think this match is the best. Also I feel I had the stronger mentality and every ball I was fighting.
'I wanted to win the match too much because this was a good chance to be in the quarter-final for the first time.
'Maybe I should play on the grass courts more often.'
Zheng has the chance to make history by becoming the first Chinese woman to reach the semi-finals of a Grand Slam. But she insisted just making it to the last eight was good enough.
'I feel getting into the quarter-final is fine. I don't want to think too much about the semi-final,' she said.
'I just want to keep going, try my best, and don't think too much. It's the first time in the quarter-finals for me. It's very good.
'I've played Vaidisova maybe two or three times but I've never won. I don't want to think too much because on grass she is very dangerous.'
Zheng was the second lowest ranked woman left in the singles but there was no sign of an inferiority complex from the Chinese in only her second Grand Slam last 16 appearance.
Her compact game has few holes and she gradually ground Szavay down and broke for a 5-3 lead in the first when the Hungarian netted a forehand.
Zheng even had the luck on her side as a fortunate netcord gave her two set points. Szavay saved both but Zheng didn't waste her third opportunity as she served out the set.
Zheng lost her concentration at the start of the second set and Szavay broke for a 3-1 lead. But she swifty regained parity with a break in the seventh game.
That was enough to shatter her 19-year-old opponent's fragile morale and Zheng broke again for a 5-4 lead and showed no nerves as she easily served out the match.
Vaidisova into last eight
Czech Nicole Vaidisova sealed her place in the Wimbledon quarter-finals for the second successive year after coming from behind to overcome eighth seed Anna Chakvetadze 4-6 7-6 6-3 on Monday.
The 19-year-old, seeded 18, had looked to be heading for the exit because of her over-hitting and shaky service games in the first set against the 21-year-old Russian.
The turning point came in the second set tiebreak, which Vaidisova took to love. That seemed to give her new confidence and she quickly stormed to a 3-0 lead in the third set. She then served out the match.
Kuznetsova is latest big name knocked out
Fourth seed Svetlana Kuznetsova went the way of numbers one, two and three as she slipped to a 6-4 1-6 7-5 defeat at the hands of Agnieszka Radwanska.
Never since seedings began in 1927 have none of the top three made it into the quarter-finals of Wimbledon, but the top four will not be represented in the last eight in 2008 after the Russian was outmanoeuvred by her teenage opponent.
Kuznetsova seemed to be in control after strolling through the second set to level at 1-1 - especially after breaking in the third - but the wily 19-year-old from Poland battled back and took the third to set up a quarter-final clash with Serena Williams.
The 23-year-old Kuznetsova got off to an inauspicious start, with 14th seed Radwanska seemingly bringing up break points at will.
A couple of lobs in the fourth and sixth games gave the Pole opportunities, but Kuznetsova's serve got her out of trouble.
She tried her luck one time too many in the eighth, though, handing Radwanska a break as she netted a passing attempt.
Kuznetsova broke back immediately, but Radwanska quickly brought up three set points on her opponent's serve, deservedly cashing in on the third with a fine backhand down the line.
Kuznetsova stormed into a 4-0 lead in the second set, taking advantage of Radwanska's weak second serve.
The teenager managed to save three set points at 5-1 down, but she sent a simple forehand wide to finally succumb.
And it seemed all over when an error and another weak second serve gave Kuznetsova three break points, the Russian looking dominant as she moved 4-1 ahead.
But the Russian netted in game seven to surrender the initiative and could not take advantage of three break points in game eight.
Radwanska went ahead for the first time in the set in game 11 after returning a fierce first serve from Kuznetsova and duly served out to send another top seed crashing out and gain revenge for her defeat to the Russian in the third round of last year's tournament.
