World No. 1 Serena Williams is on target of her title defense after winning against Lucie Safarova while fifth-seed Maria Sharapova went out of contention after a three set clash with Carla Suarez Navarro in the third round of the Rogers Cup on Thursday.

Williams staved off Safarova's challenges, coming out with a 7-5, 6-4 victory over the Czech.

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Safarova came out strong in the first set as she held serve against the defending champion to level the game at five apiece. Williams saw a chance to break Safarova's rally, coming to the net and taking the first set.

Williams found her groove in the second set, delivering furious serves that kept Safarova outside the lines.

Williams marches onto the quarterfinals Friday against Caroline Wozniaki, who demolished Shelby Rogers in two sets 6-1, 6-0.

In other matches, Sharapova had a slugfest against Navarro in a match interrupted twice by rain. Navarro upset the French Open winner, 6-2, 4-6, 6-2

Navarro, 25, got the better of the first set as she broke Sharapova's serve four times. But Sharapova rallied in the second set to force a deciding third set.

With the rain providing a respite to the intense match, Navarro gathered her wits and took the victory.

Another upset happened on Thursday as Ekaterina Makarova defeated Wimbledon vhampion Petra Kvitova in the hard courts of the Uniprix Stadium in Montreal, 6-4, 1-6, 6-2.

Makarova quickly put the second seed to a defensive position as she took the first set, breaking Kvitova twice.

But Kvitova settled down on the second set, bouncing back from her first-set loss. Makarova recovered in the third, capitalizing on the Czech's errors to snatch the match from Kvitova.

Tagsserena williams, Caroline Wozniaki, Lucie Safarova