Having opted to skip this summer's Olympic Games in Paris, Raducanu also missed WTA 1,000 events in Toronto and Cincinnati in the lead-up to the US Open

Raducanu admitted afterwards that she lacked some match sharpness against Kenin.

"I got off to a bit of a slow start, but did really well to fight back in sets two and three and there wasn’t much in it," Raducanu said.

"I think I worked my way into the match pretty well, but at this level you can’t really afford to have a slow start of the set and start from a set down.

"I know when I have a lot of matches, just like every player, you feel really good, you feel like everything's automatic.

"I can learn from it and manage my schedule slightly differently."

After an injury-plagued 2023, Raducanu returned to the tour in January and reached the second round of the Australian Open.

She skipped the clay-court French Open to focus on being fit for the British grass season - a decision that seemed to have paid off when she made an impressive run to the Wimbledon fourth round.

"I think I've made progress considering where I was at the start of the year - I didn't play for seven months," the world number 71 added.

"I had a month of December training after three surgeries so I think to climb back into the top 100 was a really good achievement."

After fending off two break points in the first game, Raducanu's serve was constantly under pressure from Kenin, who reeled off five games in a row to take the opening set.

Raducanu made a statement by breaking early in the second with a series of bruising forehand winners, but Kenin responded immediately to level at 1-1.

As the British number two grew into the match, Kenin's frustrations came to the fore and she angrily swiped a ball away right before Raducanu broke for a 3-2 lead.

Raducanu struck again at 5-3 to force a decider and made a confident start to the third set while her opponent's unforced error count mounted.

Yet it was the American who made the first breakthrough and, after being just two points away from victory on Raducanu's serve, Kenin closed out the win on her first match point.

"It was a rollercoaster match," Kenin said afterwards. "Emma is such a tough player and she played some great tennis. I'm just super happy to have won."

Like Raducanu, Kenin has struggled for form since winning the Australian Open in 2020 and reaching the French Open final in in the same year.

She will face title contender Jessica Pegula next after the sixth seed beat Shelby Rogers 6-4 6-3.

Russell Fuller, BBC tennis correspondent in New York

Kenin allowed Raducanu little room to breathe in the first set: she was the aggressor, trying to stifle her opponent from the word go.

Raducanu’s second set fight back was impressive - she extended the rallies and tempted an impatient Kenin to go for too much.

The British player looked the more likely winner early in the third set, but Kenin’s serve proved decisive.

Raducanu chose not to play any tournaments in the three weeks before this US Open, and she did not look as match sharp as she was earlier in the summer.

The 21-year-old did not disagree, and will probably approach things differently in future - saying “it’s a lesson to learn for next year.”