Kim Clijsters pumps her fist after taking the second set. (Paul Chiasson/Canadian Press)

Regular service has resumed at the Rogers Cup in Montreal, but that doesn't mean it was easy sledding by any means for one top-ranked player.

Kim Clijsters joined a number of seeds who moved on to the tournament's third round on Wednesday, but she was pushed to the limit by the 101st-ranked Bethanie Mattek-Sands before eventually prevailing 4-6, 6-4, 6-3.

What should have been an easy second-round affair for Clijsters turned into the match of the tournament in the early going, with fantastic high-pressure shot-making throughout. Clijsters, ranked fourth in the world and seeded fifth at the Rogers Cup, arrived in Montreal on the heels of a victory in Cincinnati last week and is the hottest player on the tour right now.

But Mattek-Sands, who is 97 spots below Clijsters in the world rankings, nevertheless confounded the 27-year-old Belgian with her aggressive shot-making for the first half of the match, breaking Clijsters twice in the first set to take it 6-4.

The 25-year-old American had never defeated a top-10 opponent in her career, but kept up the pressure on Clijsters in the second set. A major upset was definitely brewing when she put Clijsters down 4-1 with the reigning U.S. Open champion facing double break point.

But that's when the match swung the other way — Clijsters held her nerve and battled back to win the game and then took the next four to win the set 6-4.

The momentum went back and forth in the final set, with Clijsters and Mattek-Sands exchanging early breaks.

Mattek-Sands looked like she had Clijsters on the ropes for good, as the Belgian faced triple break point while down 3-2. But Clijsters dug deep yet again, battling back to win the game and then took the next three to advance to the third round.

If Clijsters fell, she would've joined No. 1 Jelena Jankovic on a flight home. Jankovic fell to qualifier Iveta Benesova 7-6 (3), 6-3 a day earlier.

Instead, Clijsters will face Kaia Kanepi of Estonia in the third round, as she defeated Sybille Bammer of Austria in her second-round match.

Other seeds advance

Clijsters also joined a number of other seeded players who booked their spots in the third round by earning victories Wednesday.

Caroline Wozniacki from Denmark returns to Patty Schnyder during second-round play at the Rogers Cup in Montreal on Wednesday. (Paul Chiasson/Canadian Press)No. 2 Caroline Wozniacki of Denmark overcame a tough challenge from Swiss Patty Schnyder to emerge victorious 7-5, 7-5.

Wozniacki's next opponent is No. 15 Flavia Pennetta, of Italy, who defeated Russia's Alisa Kleybanova 6-3, 6-3 on Wednesday. No. 6 Francesca Schiavone, also of Italy, moved on to the third round with a 6-4, 6-7 (5), 6-2 victory over Russia's Ekaterina Makarova.

Joining Wozniacki in the third round is defending Rogers Cup champion Elena Dementieva. The No. 4 seed from Russia was pressed by the Czech Republic's Klara Zakopalova, before finally earning a 6-2, 6-4 win.

No. 7 Agnieszka Radwanska of Poland set the tone for the seeded players, beginning the day by beating American Vania King 6-0, 6-3.

No. 17 Marion Bartoli of France had the easiest time of the seeded players. She advanced to the third round after her opponent, Kimiko Date Krumm of Japan, withdrew from the tournament with a strained left quadriceps muscle.

Date Krumm, 39, defeated Monica Niculescu of Romania in three sets Tuesday.

No. 10 Victoria Azarenka of Belarus also earned a spot in the third round with a 6-4, 6-1 win over Russia's Maria Kirilenko.

In an all-Russian matchup, Dinara Safina outlasted No. 18 Nadia Petrova 7-5, 4-6, 6-4 to book her spot in the third round.

Hungarian Agnes Szavay upset No. 13 seed Yanina Wickmayer of Belarus 6-7 (5), 6-3, 6-4.

There are no Canadians remaining in the field after the final two lost their first-round matches on Tuesday.

Russian Alisa Kleybanova, ranked No. 26 in the world, defeated Heidi El Tabakh of Oakville, Ont., 6-1, 6-2. Valerie Tetreault of St-Jean-sur-Richelieu, Que., had a quick first appearance at the Rogers Cup, losing 6-1, 6-0 in 69 minutes to Bartoli.

Fellow Canadians Aleksandra Wozniak and Stephanie Dubois were eliminated Monday on the first day of competition.

Doubles results from Wednesday:

Second Round

• Iveta Benesova and Barbora Zahlavova Strycova of the Czech Republic upset the top-seeded pair of Liezel Huber of the United States and Nadia Petrova of Russia 7-6 (0), 1-6, 11-9.
• No. 2-ranked Gisela Dulko of Argentina and Flavia Pennetta defeated Julie Coin of France and Alicja Rosolska of Poland 6-1, 2-6, 10-8.
• No. 3-ranked Kveta Peschke of the Czech Republic and Katarina Srebotnik of Slovakia defeated Daniela Hantuchova of Slovakia and Caroline Wozniaki of Denmark 6-4, 2-6, 10-3.
• Italians Sara Errani and Roberta Vinci defeated Cara Black of Zimbabwe and Anastasia Rodionova of Australia 6-4, 4-6, 10-7.
• Monica Niculescu of Romania and Shahar Peer of Israel defeated Vania King and Yaroslava Shvedova of Kazakhstan 0-6, 7-5, 10-7.
• Anabel Medina Garrigues of Spain and Zi Yan of China defeated Andrea Hlavackova and Lucie Hradecka of the Czech Republic 6-1, 6-4.

First Round

• No. 8-ranked Maria Kirilenko of Russia and Agnieszka Radwanska of Poland defeated Anna-Lena Groenefeld of Germany and Ipek Senoglu of Turkey 6-0, 7-6.