On September 2 last year, Jack Draper hung his head in despair as he was forced to retire from the third round of the US Open, after his injury-ravaged body gave up on him. Exactly a year on and on the very same court, on Saturday he held his arms out in victory after scoring the most significant win of his career to guarantee himself a place in the second week of a major for the very first time.

The 21-year-old Brit is enjoying his best-ever run at a major in reaching the US Open last 16, surviving a scare against world No 89 Michael Mmoh.

It was not easy. Draper went from a commanding two-set lead to being lured into a demanding match by his American opponent, who suddenly upped his level in the third set. But he eventually won 6-4, 6-2, 3-6, 6-3 in three hours and four minutes, thanks in part to his 51-winner count, and it was just reward for a young player who has been perennially stalled by injuries.

As he battled through, his mind wandered to the heartbreak of throwing in the towel last year during his third round match against Karen Khachanov. “I was thinking on the court today, it’s like ‘Groundhog Day’,” said Draper. “It was exactly one year on [from] playing Khachanov and I was so tired. I was carrying a bit of an injury. I’m so proud of the work that I’ve put in the last year. Even though I haven’t been able to compete too much, I generally think I’m a much better player and better all-around athlete, as well.

“To come here a year on, despite my ranking having dropped a fair bit and not being able to be on the same confidence level that I was last year, I’m incredibly proud of that and hopefully I can keep going this week.”

Such is Draper’s inexperience at this level, that he has only ever played 11 main draw matches at slams and never come through in four sets. This was the first time he had risen to that challenge, and the fact his body held up too was a relief. “I think the last couple of four-set matches I played against Rafa [Nadal] I was cramping after two sets, and also [Alex] de Minaur at Wimbledon I was cramping a lot. Today is a real confidence booster for my body, for sure.”

This result has come after the season from hell for Draper from a physical standpoint. Before this week in New York, he had not won a single match at a major this year and had retired through injury from three events – dropping from inside the top 40 to outside the top 120. His third retirement came just a week before the US Open began, when he had feared a shoulder issue may stop him from competing in the final major of the season. Getting to the start line in New York was an achievement in itself, but he is now thriving after a career-high win.

This third-round match was far more difficult than his second-round scalp against the ill 17th seed, Hubert Hurkacz. Despite his lower ranking, Mmoh has enjoyed a decent set of results this summer and came to compete. His run at the US Open has equalled his best result at a major too, after outlasting the retiring John Isner in a five-set battle on Thursday.

The 25-year-old initially looked significantly underpowered against Draper, in particular on the forehand side, and was not allowed to lean into his tenacious retrieving style, as the young Brit closed down points quickly. After Draper secured his first break in the opening set, he looked to be cruising for the next hour or so, wrapping up the first two sets with relative ease. The atmosphere was flat, the crowd fairly sparse for a match lacking in any drama.

But in the third set Mmoh came alive. His first serve percentage drastically improved from the 30s to near the 80s, and he took away Draper’s time with clever point construction. He had done similar in his second-round match against Isner, where he also trailed by two sets. Draper’s energy on the other side of the court dwindled, and Mmoh pounced with an early break. Suddenly the threat of a comeback loomed.

After sending a backhand pass wide down 4-2 and 30-30, Draper launched his racket at the ground in disgust. Mmoh’s aggressive net play was paying off, and he held on to take the set 6-3. The Grandstand crowd erupted with chants of “Let’s go Mmoh!” and that atmosphere heightened when Mmoh survived a gruelling 14-shot rally to break the Brit in the opening game of the fourth. While Mmoh fell to his back in dramatic celebration, the crowd going wild, Draper held his hands on his hips and shook his head.

That moment could have thrown him, but Draper recovered with an immediate break back. Then in the sixth game he hit a thunderous forehand to take a crucial 4-2 lead and bravely serve-volleyed on match point to clinch the landmark win.

He plays either eighth seed Andrey Rublev or Arthur Rinderknech of France for a place in the quarter-final.