Naomi Osaka fought off two match points for a three-set win over Liudmila Samsonova to reach the third round of Canadian Open on Wednesday as Wimbledon champion Iga Swiatek cruised past her opponent to also advance.

The four-time Grand Slam champion saved back-to-back match points in the 10th game of the second set, and she trailed 5-2 in the second-set tiebreaker on the way to a 4-6, 7-6 (8-6), 6-3 triumph.

Osaka, now working with Tomasz Wiktorowski after announcing on Monday she had split with coach Patrick Mouratoglou, notched her first win over a top-20 player since beating Karolina Muchova at the Australian Open.

But she had to dig deep for the win after surrendering early breaks in each of the first two sets.

Wimbledon quarterfinalist Samsonova served for the match at 5-4 in the second and led 40-15. The Russian fired a forehand long on her first match point and a lackluster drop shot effort on her second gave Osaka an opening, and the Japanese star pounced.

Samsonova's double fault on break point allowed Osaka to level the set, and after storming back in the tiebreaker to force a third set Osaka took control early, breaking Samsonova twice on the way to a 4-1 lead.

"She definitely came out really hard and, for me, I was definitely overwhelmed, and I didn't know if I should also be hitting winners," Osaka said.

"But after a while I just tried to keep the ball in court," added Osaka, who snapped a four-match losing streak in three-setters.

Osaka next faces Latvia's Jelena Ostapenko, who beat Mexico's Renata Zarazua 6-2, 4-6, 6-2.

Swiatek, seeded second in her first tournament since her crushing victory over Amanda Anisimova in the Wimbledon final, breezed past Chinese qualifier Guo Hanyu 6-3, 6-1, breaking Guo's serve six times.

Her untroubled tournament opener followed Osaka's battling victory over Samsonova.

Australian Open champion Madison Keys, the sixth seed, opened her Canadian campaign with a 6-2, 6-1 victory over Laura Siegemund, avenging a third-round loss to the German at Wimbledon.