* World number four Jankovic thrashes Tunisian Sfar
* Second seeded Serb to play Italy's Vinci in last eight
(Adds Jankovic quotes)
MADRID, April 9 (Reuters) - World number four Jelena Jankovic eased into the quarter-finals of the Andalucia Tennis Championships with a 6-3 6-0 win over Tunisia's Selima Sfar on Thursday.
The Serbian second seed, by far the highest-ranked player left in the tournament after Wednesday's shock exit of world number one Serena Williams, converted five of her 11 break points on the clay in Marbella and was broken just once.
"I feel good after the victory," said Jankovic, who will play Italy's Roberta Vinci for a place in the last four.
"It was a little bit of a slow start for me and I was moving slow and didn't react to the balls but after that I found my rhythm and I did my job," she told a news conference.
Injury-hampered Williams lost 6-4 3-6 6-1 in the first round to Klara Zakopalova, who reached the last eight on Thursday with a 7-6 5-7 6-0 win over fellow Czech Renata Voracova.
The top-seeded Williams had not recovered from a thigh problem that affected her performance in Miami last week and she was broken seven times by Zakopalova, ranked 95 in the world.
Williams will be replaced at the top of the world rankings by Russian Dinara Safina when they are updated on Monday.