Jankovic's indifferent season continues with defeat in Eastbourne
Svetlana Kuznetsova, Jelena Jankovic and Vera Zvonareva were all big-name casualties at the Aegon International after first-round exits in Eastbourne.
French Open champion and second seed Kuznetsova suffered a 6-0 6-3 defeat to Canada's Aleksandra Wozniak.
Third seed Jankovic was beaten 6-7 6-3 6-2 by Russia's Anna Chakvetadze, while fourth seed Zvonareva lost 6-3 1-6 6-3 against France's Amelie Mauresmo.
Britons Anne Keothavong and Elena Baltacha also both lost on Tuesday.
British number one Keothavong was beaten 6-3 6-2 by Austrian Sybille Bammer, while number two Brit Baltacha lost 6-2 7-5 to China's Na Li.
Keothavong said: "I expected her to be a tough opponent and I didn't give myself a chance. I was spraying balls about and she just had to put the ball in the court."
In the men's competition, Briton Josh Goodall was beaten 6-3 7-5 by Croatian Ivan Ljubicic in the second round.
The strong women's field, which featured seven of the world's top 10, saw top seed Elena Dementieva secure a comfortable 6-2 6-2 win over fellow Russian Maria Kirilenko on Monday.
But compatriot Kuznetsova was comprehensively outplayed by Wozniak, blaming her defeat on her lack of preparation on grass.
"I played for two months on clay and I have it almost in my blood," said the 23-year-old.
"I don't have to think about the tactics. I know how to defend, how to attack and what time; how to serve and this and that. And on this surface, everything is opposite. For me, it's too much to change in three days."
Chakvetadze pulled off a shock victory against Jankovic, racing to a 5-1 first-set lead before the world number six fought back to win successive five games and the all-important tie-break.
But Jankovic failed to convert break points at 1-1 and 3-3 in the second as Chakvetadze seized the initiative to close out the set.
And the world number 31 clinched the third for her first win over a top-10 opponent since beating Marion Bartoli at the Paris Indoor event in February 2008.
"I am pleased with every win right now because it's very important to me to get back my confidence," said Chakvetadze.
Kuznetsova is finding it hard to convert her clay tactics onto grass
"I lost a huge opportunity in the first set but I'm glad I came back in the second and third."
Jankovic, who began the year ranked number one in the world and playing her first match on grass this season, said she is still adjusting to the faster courts.
"It took me a while to get the rhythm out there," she said.
"And then for some reason from staying so low and getting those low balls my legs got so tight and so tired, and especially in the third set I didn't have the energy in my legs anymore to bend down."
Reigning Eastbourne champion Agnieszka Radwanska saw off younger sister Urszula 6-1 6-1, sixth seed Caroline Wozniacki beat Alisa Kleybanova 6-3 6-2 and former Wimbledon finalist Bartoli overcame Gisela Dulko 6-3 6-1.
Elsewhere in the men's, top seed Igor Andreev surprisingly lost 7-6 (8-6) 6-2 to Canadian qualifier Frank Dancevic, who will now play Britain's James Ward.