British number one Katie Boulter reached the third round of the Canadian Open in Toronto as opponent Beatriz Haddad Maia was forced to retire injured after just two games.

Haddad Maia, the world number 33 and 13th seed, received treatment for an issue with her lower back after the first game.

The Brazilian attempted to return, but retired once Boulter, 28, levelled the first set at 1-1.

Boulter, who advances to the third round of the competition for the first time, will play the winner of the game between world number three Aryna Sabalenka's match against China's Yuan Yue on Friday.

Elsewhere, American top seed Coco Guaff beat China's Wang Yafan 6-4 6-4 to set up a tie with Diana Shnaider - who knocked out Britain's Harriet Dart in the first round.

Third seed Jessica Pegula won 7-5 6-4 against Karolina Pliskova, while world number 17 Anna Kalinskaya beat Lesia Tsurenko 6-2 6-2.