The renaissance of Venus Williams continues to gather pace in view of the British public but sister Serena failed to join her in the AEGON International quarter-finals on Wednesday.

25824 - Venus powers on as Serena fades at Eastbourne

Five-time Wimbledon champion Venus confirmed that she will be a serious contender for the year's third grand slam, beating former world No. 1 Ana Ivanovic in straight sets. However, sister Serena, a four-time winner at the All England Club, displayed a clear lack of fitness as she ran out of steam in a three-hour war of attrition against top seed Vera Zvonareva.

Serena had looked hopelessly out of tune on Tuesday as she struggled through her opening match, but the reigning Wimbledon champion initially made significant strides 24 hours later, taking the first set against Zvonareva. She is still far from her pinnacle condition in the fitness department though, and after serving for the match Williams was beaten 3-6 7-6(5) 7-5 by the world No. 3.

Williams' first round match against Tsvetana Pironkova had seen her drop the opening set 6-1, and she sparked fears of a similarly poor start against Zvonareva, instantly falling to 0-30. An awesome backhand down the line helped Williams avoid an immediate break, but her serve was penetrated when Zvonareva guided a forehand down the line for 2-1.

Williams was building points nicely though and she broke back immediately, before adding some touches of class with a couple of smearing cross-court forehand winners. Zvonareva created five break chances in the set, but it was Williams who clinched the vital third break of the match thanks to a booming backhand to take the set.

The former world No. 1 was showing signs that she could return to her very best form as a caressed backhand winner earned her the first break of the second set. However, Williams was seen gasping for breath as she struggled with her fitness, and when she served for the match Zvonareva kept her moving around the court to break back. The tiebreaker then also went the way of the Russian when Williams slipped at the vital moment.

Already out on her feet, Williams had little left in the decider, quickly conceding two breaks of serve. However, the American can still compete with the best when swinging from the hip, and both players traded winners in a superb climax to the match.

Facing match point, Williams clipped a quite incredible running backhand winner that grazed the line, and she fought her way back to parity at 5-5. Zvonareva always looked fresher though, and she broke for a fourth time in the set to progress to a tie with Sam Stosur in the last eight, after the Australian beat Bojana Jovanovski 6-3 6-2.

9289 - Venus powers on as Serena fades at Eastbourne

Venus looks the more prepared of the two Williams sisters for Wimbledon, playing her way back to top form after a six-month absence from the WTA Tour, and she turned in a typically powerful display against Ivanovic, triumphing 6-3 6-2 after 62 minutes.

It was a clash of power against guile on centre court as Williams kept Ivanovic on the back foot, dropping just two points on first serve in the opening set. Ivanovic was forced to aim for the corners and use plenty of variation, producing a catalogue of sublime forehand winners in a highly entertaining match.

The telling break of the first set arrived in the fourth game when Ivanovic jabbed a backhand passing shot marginally wide of the tramline. The Serb contested the 'out' call, but the umpire would not be moved, and Williams converted the resulting break point.

Encouragingly for Ivanovic, her serve functioned much better than it has in recent weeks as she battled to stay in the match, and only a 122mph ace by Williams rescued the American from falling 2-0 behind early in the second set. Instead it was Ivanovic who was broken in the next game as unforced errors began to creep into her game, and Williams quickly wrapped up the match with a third break of the match.

Williams will now play the winner of Daniela Hantuchova and Li Na in the quarter-finals.

Former French Open champion Francesca Schiavone is out, after she was beaten in comfortable fashion 6-3 6-3 by Agnieszka Radwanska. Meanwhile, 2007 Wimbledon finalist Marion Bartoli progressed 6-3 6-3 against Maria Jose Martinez Sanchez.

At the UNICEF Open, fourth seeded Italian Flavia Pennetta was beaten 6-3 6-4 by former Wimbledon semi-finalist Jelana Dokic, but fifth seed Dominika Cibulkova strolled past Kristina Barrois 6-0 6-1 and third seed Yanina Wickmayer edged out Arantxa Parra Santonja 6-7(4) 7-6(4) 7-5.