TORONTO (Reuters) - Justine Henin may have lost some fitness during a month's lay-off but none of her trademark tenacity as she battled into the quarter-finals of the Toronto Cup with a 7-5 6-2 win over China's Peng Shuai yesterday.

Playing her first event since a semi-final loss at Wimbledon, the feisty Belgian world number one lacked her usual precision but there was no shortage of determination as she needed two bruising sets and nearly two hours in gusty, difficult conditions to tame her 58th-ranked opponent.

"It was tough I can tell you," Henin, told reporters. "For players it was terrible conditions, it's tough especially when you don't have a lot of matches.

"I was feeling better in the second set, I was a bit more relaxed and could deal a bit better with the conditions."

Henin, who has reached the final on her last two visits to Canada, winning the title in 2003, will take on Nadia Petrova for a place in the semi-finals.

The sixth-seeded Russian advanced with 6-4 6-1 win over 10th seed Patty Schnyder of Switzerland.

"I don't want to look too far ahead, I'm still in preparation for the US Open and I don't want to forget that," said Henin. "I go match after match, a little mistake can be expensive."