TORONTO -- Defending champion Ana Ivanovic lost to Yan Zi 6-3, 6-1 on Wednesday in the second round of the Rogers Cup.
Ivanovic, the No. 4 seed, was stunned by the 169th-ranked player in the world, capping a day of upsets that also claimed fifth-seeded Anna Chakvetadze and No. 8 Elena Dementieva.
"She's my favorite player," the 22-year-old Yan said. "I think today I'm really lucky."
She jumped on a lethargic Ivanovic, who won last week's East West Bank Classic in Los Angeles. Yan kept Ivanovic running with powerful two-handed strokes, never giving the 19-year-old Serb time to get comfortable.
"She played extremely well today," said Ivanovic, who won the tournament last year in Montreal. "I expected a tough match, but from the first point on she played very aggressively and she was dominating."
Yan came into the match relaxed, figuring she didn't have much to lose against a heavy favorite.
"Because she's the top player, I [didn't] think I could win," said Yan, who will take on Eleni Daniilidou on Thursday. "So [I] just went on the court and enjoyed the match."
Top seed and world No. 1 Justine Henin defeated Andreja Klepac 6-3, 6-1 in an evening match. Henin will next face Shuai Peng, ranked 58th.
Henin, who hasn't played since losing to Marion Bartoli in Wimbledon semifinals, said she was a bit rusty at the beginning of her match.
"I was playing too short, I wasn't aggressive at all at [the beginning] because it was my first game in a few weeks," she said.
Chakvetadze trailed 6-7 (5), 0-2 in her second-round match when she was forced to retire with flulike symptoms.
Sixth-seeded Nadia Petrova eliminated Canada's Stephanie Dubois with a three-set victory on a sunny, windy afternoon at the Rexall Centre. Sybille Bammer knocked off another Canadian, Aleksandra Wozniak, 6-4, 6-2.
Petrova started slowly but rebounded for a 6-7 (4), 6-2, 6-1 victory. The Russian is ranked ninth in the world, 106 spots ahead of the 20-year-old Dubois from Quebec.
In the late match, second-seeded Serb Jelena Jankovic cruised past tired Canadian Marie-Eve Pelletier 6-0, 6-1.
Francesca Schiavone defeated Dementieva 6-7 (5), 6-3, 6-2 in a mild upset and No. 16 seed Lucie Safarova was ousted by Meghann Shaughnessy 3-6, 6-4, 7-5.
Schiavone isn't seeded but at No. 26, is only nine spots behind Dementieva in the world rankings. Dementieva double-faulted 13 times and had only one ace.
Bartoli, the No. 7 seed, was up 6-2, 2-1 when Maria Kirilenko retired. Also advancing were No. 9 seed Dinara Safina, No. 10 Patty Schnyder and No. 12 Tatiana Golovin.
Safina beat Nathalie Dechy 6-1, 6-2; Schnyder downed Flavia Pennetta 6-3, 6-2; and Golovin eliminated Dominika Cibulkova 6-4, 6-3.