Los Angeles - Former world No 1 Victoria Azarenka, who was playing for first time since retiring in the San Jose quarter-finals, kicked off her WTA Montreal tournament on Tuesday by thrashing Kristina Mladenovic in straight sets.
Azarenka punched her ticket to the second round with a dominating 6-0, 6-1 victory in just 55 minutes over the former world number 10.
"I feel better," she said. "It was definitely pretty bad in San Jose to have such a sudden thing with my back.
"I was hoping it would be nothing serious, but sometimes when you're in the moment and get a really bad spasm, there's nothing you can do.
"I didn't really practice much after. I've only had one practice session this week."
Azarenka, who needed a wildcard to get into the Montreal draw, moves on to the second round where she will face British No 1 Johanna Konta.
Azarenka stormed through the first nine games of the match before France's Mladenovic got on the board.
The two-time Australian Open champion Azarenka eventually rolled through the final three games to get the victory in her first Montreal appearance since 2014.
Elsewhere, Maria Sharapova made quick work of Bulgarian qualifier Sesil Karatantcheva, easily winning 6-1, 6-2 in a renewal of their former teenage rivalry.
"No matter what tournament or who you're playing against, you have to figure things out as you go. I think I did a good job of that today," Sharapova said.
Sharapova, a finalist in 2009, performed solidly, defeating Karatantcheva for the fifth time in their five career meetings.
"I was aggressive, I served well throughout the match," Sharapova said. "I think I did everything a little bit better, especially towards the end of the match."
The pair were facing each other for the first time in eight years. They played their first three career matches as teenagers, including a fiery affair on the outer courts at the 2004 Indian Wells tournament.
World No 229 Karatantcheva was competing in her first WTA Tour main draw of the season.
Sharapova next faces another Frenchwoman Caroline Garcia, who is ranked sixth in the world. Garcia came from behind to defeat Magdalena Rybarikova in three sets 4-6, 6-1, 6-3 on Tuesday.
Results of the WTA tournament in Montreal on Tuesday (x denotes seeded player):
Anastasia Pavlyuchenkova (RUS) bt Christina McHale (USA) 6-3, 6-2
Sorana Cirstea (ROU) bt Monica Niculescu (ROU) 3-6, 6-4, 6-4
Maria Sharapova (RUS) bt Sesil Karatantcheva (BUL) 6-1, 6-2
Alize Cornet (FRA) bt Tatjana Maria (GER) 4-6, 6-1, 6-3
Alison Van Uytvanck (BEL) bt Sofya Zhuk (RUS) 6-1, 6-2
Ashleigh Barty (AUS x15) bt Irina Begu (ROU) 6-3, 1-6, 7-5
Kiki Bertens (NED) bt Carol Zhao (CAN) 6-1, 6-2
Carla Suárez (ESP) bt Naomi Osaka (JPN x16) 7-6 (7/2), 6-2
Mihaela Buzarnescu (ROU) bt Wang Qiang (CHN) 6-2, 7-5
Johanna Konta (GBR) bt Jelena Ostapenko (LAT x11) 6-7 (6/8), 6-1, 6-2
Elise Mertens (BEL x14) bt Eugénie Bouchard (CAN) 6-2, 6-4
Aryna Sabalenka (BLR) bt Ana Bogdan (ROU) 6-4, 4-6, 6-3
Darya Kasatkina (RUS x12) bt Maria Sakkari (GRE) 6-4, 4-6, 6-1
Françoise Abanda (CAN) bt Kirsten Flipkens (BEL) 6-3, 6-2
Victoria Azarenka (BLR) bt Kristina Mladenovic (FRA) 6-0, 6-1
Zhang Shuai (CHN) bt Barbora Krejcíková (CZE) 7-5, 7-5
Caroline Garcia (FRA x6) bt Magdaléna Rybarikova (SVK) 4-6, 6-1, 6-3
Petra Kvitova (CZE x8) bt Anett Kontaveit (EST) 6-3, 6-4
Julia Görges (GER x10) bt Lucie Safarova (CZE) 2-6, 6-4, 6-3