Rafael Nadal turned in a workmanlike performance Monday at the US Open on the Ashe showcourt as the Spaniard defeated Denis Istomin 6-1 6-4 6-2.

The 2013 champion won his 44th match of 2016, an effort which the 30-year-old characteriSed as average “not very good, not very bad”.

Nadal ran his record in New York first-round contests to 12-0 while Istomin has now lost 21 straight matches against top-10 opponents.

Nadal could not avoid queries about the left wrist injury that forced him from the game during the French Open.

“It’s not easy to go two months-and-a-half out of competition in the middle of the season without hitting a forehand,” he said.

“I need to have the confidence again with my wrist. That is coming, I feel the wrist much better, and every day I feel that the wrist a little bit better.”

The 2014 winner and Cincinnati champion Marin Cilic showed his seventh seed status by beating Rogerio Dutra Silva 6-4 7-5 6-1.

Gael Monfils found his trademark athleticism a bit too strong for a courtside clock in a defeat of Gilles Muller 6-4, 6-2, 7-6 (7-5).

The 10th seed leapt up to retrieve a shot and crashed a foot into the two-metre square apparatus.

A second later, the computerized works fell onto the court in a mass of circuits and semi-conductors, splintering the glass and leaving the clock totalled.

“When you are in the moment you don’t feel really anything. Just jump. I saw a wall, it was quite lucky. It hurt me a little bit,” Monfils said.

“It could have been pretty bad, could have fallen on my ankle or calf.”

Compatriot and 13th seed Richard Gasquet was dispatched in a 6-2, 6-2, 6-3 upset by British outsider Kyle Edmund.

The 21-year-old Brit won 6-2 6-2 6-3 on Monday against the 2013 US Open semi-finalist.

Edmund, ranked 84th, had 40 winners, 21 on his forehand. He has twice made it to the second round at the French Open.

Gasquet hadn’t lost in the first round at a major since 2010 at Roland Garros.

Meanwhile, 2014 champion Marin Cilic is through to the second round with a straight-set win.

The seventh-seeded Cilic beat 108th-ranked Rogerio Dutra Silva 6-4 7-5 6-1 despite posting more unforced errors than winners (24-23).

Cilic is coming off his first Masters title, beating Andy Murray in the final at Cincinnati.

Dutra Silva is now 0-3 against top-10 players. He came in 3-3 in his career at the US Open and 0-5 in the other majors.