(CNN) -- Serena Williams has been beaten in her comeback event in Eastbourne, losing a tight three-set second round match to top seed Vera Zvonareva on Wednesday.
American Williams has not played in a competitive tournament since defeating Zvonareva in the Wimbledon final a year ago.
However, the Russian claimed some revenge for that loss, recovering from dropping the opening set to secure a 3-6 7-6 7-5 triumph after three hours of intense tennis.
Zvonareva, who has been seeded second for Wimbledon next week, paid tribute to Wiliams after the match, telling the official WTA Tour website: "Serena has done an unbelievable job coming back after almost a year of not playing.
"She spent more than three hours on the court playing some unbelievable tennis. She's a great champion and I have a lot of respect for her."
Williams was appearing in Eastbourne for the first time after two operations on a foot she cut on broken glass in a restaurant, followed by further surgery in February to remove blood clots from her lungs.
Meanwhile, older sister Venus kept the Williams flag flying high on England's south coast, reaching the quarterfinals with a comfortable straight sets win over Ana Ivanovic.
Venus, who has been out of action for five months with an abdominal injury, went through 6-3 6-2 and told the WTA Tour website: "I was happy to have some clean service games and not a lot of errors.
"I feel I'm playing well on the big points -- these matches have been crucial for me to get back, literally, into the swing of things."
In other matches, third seed Victoria Azarenka beat the final British player, Elena Baltacha, 6-1 7-6, while Czech fifth seed Petra Kvitova saw off defending champion Ekaterina Makarova 7-6 7-6.
In the men's draw, Bulgarian Gregor Dimitrov upset South African sixth seed Kevin Anderson 6-3 6-2, while third seed Janko Tipsarevic beat British number two Jamie Ward -- who reached the semifinals at Queen's Club last week -- 6-3 4-6 6-2.
Top seed Jo-Wilfried Tsonga, from France, who was betean in the final at Queen's by Andy Murray, lost 6-2 6-3 to Czech Radek Stepanek.
Meanwhile, American Sam Querrey, who won at Queen's in 2010, has been forced to withdraw from Wimbledon due to an arm injury.