San Diego, California :Fifth-seeded Italian Flavia Pennetta defeated Maria Kirilenko 6-4, 7-6 (7/5) on Thursday to reach the quarter-finals of the WTA San Diego Open.
Pennetta notched to early breaks to pocket the opening set, then fell behind 5-2 in the second.
She responded by winning four straight games, but was broken at love when serving for the match at 6-5.
Kirilenko saved one match point at 6-4 in the tiebreaker before Pennetta was able to close it out.
"After the first set, I just relaxed a little bit," Pennetta said. "She was making some mistakes at the end of the first set so I was thinking she was going to do the same.
"But she started to play better and more aggressive. I was a little too far from the (base)line and I was running too much."
Pennetta will face second-seeded Australian Samantha Stosur in the next round.
"I have to rest now and be ready for running so much," Pennetta said. "When she hits the ball it's really powerful. My return is going to be really important."
In another second-round match, Slovakia's Daniela Hantuchova defeated China's Zheng Jie 6-2, 6-1.
Third-seeded Vera Zvonareva of Russia was cap the day taking on local teenager Coco Vandeweghe in a second round match.