Toronto - Russian qualifier Daniil Medvedev upset 13th-seeded American Jack Sock 6-3, 3-6, 6-3 in the first round of the Rogers Cup on Monday.
Canada's Milos Raonic, who has fallen from No 3 to No 30 due to numerous injures the past two seasons, also advanced with a 6-3, 6-4 win over David Goffin of Belgium after heavy rain delayed play for nearly three hours.
Raonic used his powerful serve to his advantage, firing 13 aces to Goffin's two and won 100 percent of his first serves. He will next play the winner of a match between American Frances Tiafoe and Italy's Marco Cecchinato.
In doubles play, Novak Djokovic and Kevin Anderson defeated Canadian teens Denis Shapovalov and Felix Auger-Aliassime 6-3, 6-2.
Shapovalov and Auger-Aliassime started the match strong before Djokovic and Anderson took control. They broke Anderson's serve for a 2-0 lead, to the delight of a tightly packed grandstand crowd.
However, the Wimbledon finalists team - nicknamed Djokerson thanks to a Twitter poll conducted by Djokovic earlier in the day - broke back to tie the match 2-2, and again to go up 5-3.
Anderson and Djokovic won five straight games, going up two breaks, to win the second set.
In other singles matches, American Bradley Klahn topped Spain's David Ferrer 7-6, 6-4; Pierre-Hughes Herbert of France got past Spaniard Albert Ramos-Vinolas 4-6, 6-3, 6-4; Benoit Paire of France defeated Jared Donaldson 6-3, 6-4; and Ilya Ivashka of Belarus beat Yuichi Sugita of Japan 6-2, 6-3.
Also, 30-year-old Canadian Peter Polansky, a wild card entry playing in the morning draw, defeated Matthew Ebden of Australia 7-6 (3), 6-4. He will play the winner of a match between Djokovic and Hyeon Chung of South Korea in the second round.
Results from the ATP Toronto Masters tournament on Monday (x denotes seeding):
Benoit Paire (FRA) bt Jared Donaldson (USA) 6-3, 6-4
Peter Polansky (CAN) bt Matt Ebden (AUS) 7-6(7/3), 6-4
Illya Ivashka (BLR) bt Yuichi Sugita (JPN) 6-2, 6-3
Fernando Verdasco (ESP) bt Peter Gojowczyk (GER) 6-2, 6-2
Marton Fucsovics (HUN) bt Joao Sousa (POR) 6-4, 7-6(7/2)
Daniil Medvedev (RUS) bt Jack Sock (USA x13) 6-3, 3-6, 6-3
Bradley Klahn (USA) bt David Ferrer (ESP) 7-6 (7/5), 6-4
Pierre-Hugues Herbert (FRA) bt Albert Ramos (ESP) 4-6, 6-3, 6-4
Pablo Carreno-Busta (ESP x12) bt Yoshihito Nishioka (JPN) 6-0, retired
Diego Schwartzman (ARG x11) bt Kyle Edmund (GBR) 6-1, 6-2
Milos Raonic (CAN) bt David Goffin (BEL x10) 6-3, 6-4
Borna Coric (CRO) bt Vasek Pospisil (CAN) 6-4, 6-3