WIMBLEDON, England (AP) — Playing Olympic tennis twice a day proved

too much for Venus Williams. Her workload at Wimbledon will now be

a little lighter.

Williams squandered a lead in each set yesterday and lost her third-round match to No 7-seeded Angelique Kerber of Germany, 7-6 (5), 7-6 (5).

Williams, seeking a record fourth gold medal in Olympic tennis, still has a shot with her

sister Serena in doubles, where they're in the quarter-finals.

Venus looked sharp in the first two rounds of singles, as if rejuvenated by the setting, where she has won five of her seven Grand Slam titles. But she was diagnosed in 2011 with an

auto-immune disease that causes fatigue, and looked weary against Kerber.

In the first set Williams failed to convert three set points, then blew a 5-1 lead in the tiebreaker. She was up 3-1 in the second set, but Kerber again charged back.

Kerber, a semi-finalist at Wimbledon last month and at the US Open last year, is ranked

a career-high No 7. She advanced to the quarter-finals against top-seeded Victoria Azarenka of Belarus.

Also reaching the final eight was Serena Williams, who hit 12 aces and repeatedly rocketed her groundstrokes past No 13-seeded Vera Zvonareva to win 6-1, 6-0.