All Monday, Wimbledon bombarded the senses with an overload of tennis, an embarrassment of must-see matchups held from early afternoon to evening, from Centre Court to Court 18. By the end, both Williams sisters had muscled into the quarterfinals. So had both defending champions (Serena Williams, Roger Federer). Top seeds dispensed beatings (Federer rolled, 6-3, 6-2, 6-3), and took them (third-seeded Caroline Wozniacki managed two games, total, against Petra Kvitova) and retired because of injury (Jelena Jankovic, fourth seed, back). Kim Clijsters even won the battle of the Belgians who left tennis and returned, defeating Justine Henin, 2-6, 6-2, 6-3. 'A wonderful day,' Federer called Wimbledon's second Monday, and it was, for tennis fans and ticket holders and the 16 players who advanced. Tennis aficionados often rank this Monday as the best day on the sport's calendar. This year, 24 seeded players remained at the beginning of the second week, including 15 seeded 10th or better. By the end, on the hottest, in temperature, day at Wimbledon this tournament, a few themes continued to emerge. Serena Williams again served at a frightening, almost unbeatable level. Maria Sharapova, even in defeat, showed additional signs of her career comeback. Venus Williams, quietly, moved forward once again, by beating Jarmila Groth. Meanwhile, the top men's seeds, one after another, continued to struggle, most notably No. 5 Andy Roddick, who fell to the unseeded Yen-Hsun Lu of Taiwan. But most advanced, including Novak Djokovic, who tore part of his shirt in celebration after dispatching Lleyton Hewitt, a popular upset pick, in four sets. 'There wasn't a lot of room for error,' Venus Williams said. Jo-Wilfried Tsonga, seeded 10th, took a four-set victory and pronounced his once injured back now healed. Tomas Berdych, seeded 12th, also needed four sets, and in victory, he drew Federer on Wednesday. Promising tennis still lay ahead. Seeds fell, champions rose, the fields were cut again in half. It was only Monday, but here at Wimbledon, the action had picked up. 