There was a telling moment at the end of the first set, when young Canadian Gabriel Diallo danced back to his chair after having just won the tiebreak to take an unexpected lead over 14th-seeded American Tommy Paul.
As he crossed his opponent, Diallo clenched his fists and shouted at his coach in the stands. Paul looked up at him and grinned back as if to say, ‘Just you wait.’
Fast forward 39 minutes and parity was quickly restored. Paul jogged back to his seat and it was his turn to celebrate. Diallo came back down to earth with a punch, a reminder that Grand Slams can humble you very quickly.
Ultimately, Paul did what was needed in a crowded Louis Armstrong Stadium, beating his 22-year-old opponent in four sets to secure a place in the last 16 and secure his $325,000 prize money.
The American started slowly against an opponent he had never played before, taking over an hour to get the hang of things before he could finally get going.
Tommy Paul roars with joy after winning the second set and leveling the match
Paul proved to be too much of a match for young Canadian qualifier Gabriel Diallo on Saturday
It was quite a ride for Diallo, the qualifier with a Guinean father and a Ukrainian mother, who had honed his skills on the American college stage in Kentucky and was just one match point away from not even reaching the main draw of his first US Open.
At 6ft 3in and with a great serve, few players make facing the net a challenge, but his lack of experience was clearly visible under the bright lights of the show courts in the biggest match of his career to date.
Earlier in the week he played two tough matches, first beating Jaume Munar and then stunningly defeating 24th-seeded Frenchman Arthur Fils in front of a packed Court 17.
In the first week of the tournament he was on court three hours longer than Paul, and that may have been noticeable in the third round that took place on Saturday.
The first set was a grind, with neither player able to hold serve. Paul broke to take a 4-3 lead, before Diallo broke back to level the score at 4-4. Paul then broke again, and Diallo did the same. From there, another break from Paul, and another for Diallo. Six in a row to take the first set to a tiebreak.
Serena Williams (left) was at the house to watch Paul’s victory over Diallo over Louis Armstrong
Diallo had already spent seven hours on court during his first two matches at the US Open
After that, and Diallo’s ecstatic celebration, the tide began to turn in the American’s favor. Apart from a small section of Diallo fans at the back of the bottom tier, this was a partisan home side, all fighting for the man who grew up just 100 miles away in New Jersey.
In the second set, the mistakes started to hit Diallo, who quickly fell behind 3-0 and eventually went down 6-3. Things got worse in the third set, when Paul won 6-1 and really showed his dominance in the match.
Credit to Diallo, he regrouped and kept pace with his rival, taking him to a tiebreak in the fourth to tease the possibility of a deciding set. How the fans enjoyed that.
More tough tests await Paul, who will face world number 1 Sinner in the last 16
Unfortunately, Paul improved his game and won 7-3, deciding the match with Diallo’s serve and a beautiful forehand winner.
Now it’s time for the American to look ahead, and as for the last 16 Grand Slams, the draw doesn’t get much clearer than this. No Djokovic, no Alcaraz, and 10 of the top 20 seeds already on flights home from New York.
The problem for Paul? Jannik Sinner, the best player in the world, is next.
By reaching the fourth round he equalled his best ever performance at the US Open, but now the real work begins.