Top-ranked Novak Djokovic beats American Jack Sock 6-2, 6-1 in Montreal

Jack Sock, of the United States, reacts during his match against Novak Djokovic, of Serbia, at the Rogers Cup men's tennis tournament in Montreal, Thursday, Aug. 13, 2015. (Paul Chiasson/The Canadian Press via AP) MANDATORY CREDIT (The Associated Press)

Novak Djokovic, of Serbia, reaches back to serve to Jack Sock, of the United States, during the Rogers Cup men's tennis tournament in Montreal, Thursday, Aug. 13, 2015. (Paul Chiasson/The Canadian Press via AP) MANDATORY CREDIT (The Associated Press)

MONTREAL – Top-ranked Novak Djokovic beat American Jack Sock 6-2, 6-1 on Thursday in the third round of the Rogers Cup.

Djokovic took only 54 minutes to finish off the 35th-ranked Sock.

"I never played him before, so it took me some time to figure out what his patterns are," Djokovic said. "I've watched him many times before, but it's different standing on the court."

The Serb, the tournament champion in 2007, 2011 and 2012, has won 50 of 53 matches this year.

Second-seed Andy Murray also advanced, beating Luxembourg's Gilles Muller 6-3, 6-2. The Scotsman broke Muller's serve four times in the 65-minute match.

In the night session, seventh-seeded Rafael Nadal of Spain faced Russia's Mikhail Youzhny, and fourth-seeded Kei Nishikori of Japan met Belgium's David Goffin.

Djokovic shut out Sock in the first game. With Djokovic leading the first set 3-2, Sock hit a ball long on break point. Djokovic broke Sock's serve again in the final game to take the set.

"The turning point was the 3-2 game when I made a break," Djokovic said. "After that I just felt in control of the match. I was returning very well. I neutralized his serve, which is one of his biggest weapons."

In the second set, Sock made another unforced error on break point to go down 3-1. Djokovic started the final game of the second set with a beautiful drop shot, and Sock sent his return long on triple match point.

Djokovic will face Latvia's Ernests Gulbis in the quarterfinals. Gulbis beat American Donald Young 6-4, 6-4.

Also, France's Jeremy Chardy beat Croatia's Ivo Karlovic 4-6, 7-6 (1), 6-4.