British number one Jack Draper says he was "almost a bit happy" to drop a set as he was put through a severe examination of his fitness on his US Open return.

Draper needed to dig deep to beat Argentine qualifier Federico Agustin Gomez 6-4 7-5 6-7 (7-9) 6-2 in the first round.

The fifth seed, who reached the New York semi-finals last year, was playing his first singles match since Wimbledon in early July after suffering an arm injury.

"I needed tennis in my legs. I needed to play a three-hour match," Draper said.

"I was almost a bit happy when I lost the third because my level wasn't amazing.

"Then I felt like towards the end of the fourth I started to get better and better."

Draper, 23, is seen as one of the contenders for the title on his return to the scene of his breakout Grand Slam run.

While not quite at his reliable and powerful best, the left-handed Englishman was ultimately content with how he largely negated Gomez's explosive game.

Draper soaked up a lot of pressure at the baseline, asking questions that his 203rd-ranked opponent was not able to answer consistently.

After saving a match point in the tie-break, Gomez managed to extend the contest before Draper regrouped to seal victory with his second match point.

"I wasn't too sure if I was going to make it here," Draper said when asked about the injury.

"I'm not putting too much expectation on myself. I'm so happy to be able to compete."

Fellow Briton Cameron Norrie is also through to the second round after American opponent Sebastian Korda was forced to retire injured.

How arm injury affected Draper

All eyes were on Draper's upper left arm as he took to the singles court for the first time since a shock Wimbledon second-round exit almost eight weeks ago.

The attention was not necessarily to evaluate his beefed-up muscles, but to see if there were any issues with the bruised humerus that has troubled him recently.

Draper did not play the recent ATP 1000 events in Toronto and Cincinnati to give himself time to recover, but competed in last week's revamped US Open mixed doubles competition to build sharpness.

On his singles return, Draper wore a compression sleeve, which provides support and comfort on his troublesome serving arm.

Draper insisted before the match that he would not hold back, although his serve speeds were slightly slower than usual.

"I've definitely had to rein in my serve a little bit to keep the pain down," he said.

"At the same time, though, I feel like my accuracy is almost a bit better."

An average of 111mph in the first set, dropping to 108mph, 110mph and 106mph in the next three, indicated he was not going full throttle.

The precision of Draper's kick serve contributed to not being broken until the end of the second set – which he went on to win – and was crucial again as he dominated the fourth.

While his forehand winners were outnumbered by Gomez's own blistering weapon, there were gasps when he did produce ferocity off that wing.

Flatter hitting from that side in the fourth brought Draper more success as he teed up a second-round clash against Belgium's Zizou Bergs – another explosive, fearless opponent.

'Nervous' Norrie through after Korda retirement

A "nervous" Norrie was worried about being first on court at 11:00 local time and need to fuel up before playing an opponent who was ranked inside the top 20 a year ago - and against whom he had lost three of four past meetings.

Ultimately the 30-year-old did not need to be overly concerned, as Norrie was leading 7-5 6-4 when Korda, 25, ended the match early.

American Korda only returned to tour action last week following a near three-month shin stress fracture lay-off.

He called a medical timeout at the start of the second set against Norrie when he appeared to be struggling with an abdominal issue.

Although Korda persevered for the remainder of the set he was unwilling to go any further, sending Norrie through to face Argentina's Francisco Comesana.

"I was very nervous for the match," said Norrie.

"Playing a Grand Slam match at 11am and trying to get rice down at 10am is not easy!"