Andy Murray, Stan Wawrinka untroubled at US Open

World number two Murray, expected to challenge strongly for the title at Flushing Meadows, was too good for Marcel Granollers on a rainy day in New York.

Wawrinka had more of a battle against Alessandro Giannessi before progressing at the expense of the Italian.

Kei Nishikori, Nick Kyrgios, Juan Martin del Potro, David Ferrer and Grigor Dimitrov also won.

MURRAY, WAWRINKA ADVANCE

Murray, aiming for his fourth grand slam, did what was expected of him, beating Spain's Granollers 6-4 6-1 6-4.

Wawrinka crunched 57 winners in his victory, but was pushed before getting past Giannessi 6-1 7-6 (7-4) 7-5.

Runner-up in 2014, Japanese sixth seed Nishikori overcame Russian Karen Khachanov 6-4 4-6 6-4 6-3.

While Kyrgios and Del Potro advanced without dropping a set against Horacio Zeballos and Steve Johnson respectively, Dimitrov was tested in a 4-6 6-4 3-6 6-4 6-2 win over Jeremy Chardy.

LOPEZ, SIMON OUT

Joining Johnson as a seeded departure was Feliciano Lopez, the Spaniard going down to Joao Sousa 6-2 6-4 1-6 7-5.

After four hours, 54 minutes, Gilles Simon also fell, losing to Paolo Lorenzi 3-6 6-2 6-2 6-7 (1-7) 7-6 (7-3).

German Alexander Zverev was also beaten, Daniel Evans overcoming the 27th seed 6-4 6-4 5-7 6-2.

MURRAY CHALLENGED, NISHIKORI HAPPY

Murray found it challenging playing under the Arthur Ashe roof, saying: "You can't hear anything, really. You could hear the line calls, but not so much when he was hitting the ball or even when you're hitting the ball, really, which is tough purely because we're not used to it. That's what makes it challenging."

Nishikori is satisfied with his form as he looks for another deep run at the year's last grand slam. "I think I'm getting closer to 100 per cent," he said. "I'm feeling good physically and also mentally. You know, tennis, I think it's going to come after a couple matches. I think I'm in great shape and hope I can go second week."

DJOKOVIC, NADAL TAKE CENTRE STAGE

All eyes will be on Novak Djokovic and Rafael Nadal in their respective third-round matches against Mikhail Youzhny and Andrey Kuznetsov. Marin Cilic faces Jack Sock, while John Isner is also in action.