Many of the year's most memorable upsets came on the Grand Slam stages, including big wins from a home favourite at the Australian Open and a pair of rising stars at the US Open.
As we continue to look back at the 2023 season, ATPTour.com counts down the five biggest shocks at the majors this year — all of which came in five sets.
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5) Roland Garros R1, Seyboth Wild d. Medvedev 7-6(5), 6-7(6), 2-6, 6-3, 6-4
Brazilian qualifier and Roland Garros debutant Thiago Seyboth Wild scored his first Grand Slam main-draw win in style with a upset of second seed Daniil Medvedev — who entered on a six-match clay-court winning streak after claiming his first tour-level title on the surface in Rome.
Coming into the match at No. 172 in the Pepperstone ATP Rankings, an aggressive Seyboth Wild made a dream start and held two set points for a two-set lead. But after cramping earlier in the second set, the 23-year-old could not prevent Medvedev from levelling the match and storming through set three soon after.
Undeterred, Seyboth Wild rediscovered his attacking game to surge through the final two sets. After four hours, 15 minutes, he closed out the upset with a big forehand winner, finishing with a 69 per cent win rate (38/55) on net points.
"I have watched Daniil play for my entire junior career, up until today. Playing on this court against this kind of player and beating him is a dream come true," said the Brazilian. "Walking on court I just wanted to get to the net as much as possible and use my forehand against his and it worked pretty well."
Seyboth Wild won four ATP Challenger Tour titles in 2023 — two either side of Roland Garros — and reached a career-high Pepperstone ATP Ranking of No. 74 in September.
What an upset! 🤯
Qualifier Seyboth Wild 🇧🇷 takes out the No. 2 seed, Daniil Medvedev, in 5 sets! 👏@rolandgarros | #RolandGarros pic.twitter.com/hiUHTRwZR7
4) US Open R2, Zhang d. Ruud 6-4, 5-7, 6-2, 0-6, 6-2
Zhang Zhizhen continued his rapid rise on the ATP Tour with a helping of Grand Slam revenge against returning US Open finalist Casper Ruud.
Earlier in the season, the Chinese star was beaten by Ruud at Roland Garros, where the Norwegian reached the final for the second straight year. But Zhang ensured there would be no repeat final run for Ruud in New York by notching the biggest win of his career against the fifth seed.
With the help of 59 winners, including 18 aces, Zhang became the first Chinese man to earn a Top 5 win since the start of the Pepperstone ATP Rankings in 1973. By riding his powerful forehand and serve, Zhang made up for his US Open heartbreak in 2022, when he missed out on seven match points in a first-round defeat to Tim van Rijthoven.
"Last year at the US Open, I can say it was a bad memory. But this year is a little bit different," said the 27-year-old, who went on to finish the season inside the Top 60.
Photo: Sarah Stier/Getty Images
3) Roland Garros R1, Altmaier d. Sinner 6-7(0), 7-6(7), 1-6, 7-6(4), 7-5
In a five-hour, 26-minute marathon, Daniel Altmaier saved two match points in the fourth set before Jannik Sinner erased four in the match's final game. The German claimed the first five-set win of his career by serving out the victory at the second time of asking, ending the Roland Garros run of the in-form eighth seed, who reached the semi-finals in Monte-Carlo and the quarters in Barcelona.
Altmaier showed nerves of steel to save 15 of 21 break points and supreme endurance to recover after Sinner appeared to take command of the match in a one-sided third set. The victory also avenged a five-set defeat to the Italian in the pair's only previous Lexus ATP Head2Head meeting at the 2022 US Open.
"The competition says it all," Altmaier said after moving on to the third round in Paris for the second time. "We’ve had historic matches with so many match points… I don’t know if you can call this an ‘historical’ match, but I think it was one to remember."
Photo: Julian Finney/Getty Images
2) Australian Open R2, Popyrin d Fritz 6-7(4), 7-6(2), 6-4, 6-7(6), 6-2
There was a wave of American success this year in Melbourne, but on his home turf, Alexei Popyrin made sure Taylor Fritz did not join the party. The fiery Aussie scored the standout shock of an upset-filled Australian Open with a big-serving display in Melbourne — a result made all the more surprising by the opponents' contrasting fortunes in the previous season.
Popyrin earned just five tour-level wins in 2022 but kickstarted the new campaign with his fourth Top 10 win and his second at the Australian Open (d. Dominic Thiem in 2019). Behind 19 aces, Popyrin reached the third round for the third time at his home major. He faced just two break points in a match of razor-thin margins — one in the fourth and fifth sets — and recovered after missing out on a match point in the fourth-set tie-break.
"This is the dream for me, and I don't want to wake up at all," he said in an emotional on-court interview. Just before that, he addressed the crowd as they chanted his name: "You guys were just incredible. Oh my god, this is crazy. I really couldn't have done it without you guys. This win means so much to me."
1) US Open R2, Stricker d. Tsitsipas 7-5, 6-7(2), 6-7(5), 7-6(6), 6-3
On the same day as Zhang's Ruud upset, Dominic Stricker scored his maiden Top 10 win to add to Stefanos Tsitsipas' US Open woes. The 21-year-old qualifier, who capped his breakthrough season at the Next Gen ATP Finals presented by NEOM, advanced to the third round at a major for the first time with a gutsy performance in his New York main-draw debut.
In a four-hour, 10-minute epic, the lefty battled back from 3-5 in the fourth set and played his best tennis down the stretch to keep the seventh-seeded Tsitsipas in search of his first US Open fourth-round appearance. Stricker lost just four points on his first serve (19/23) in the final set and struck 78 winners in the marathon match.
"I came out today pretty well. I felt good from the first set on. It was a tough battle but I am just super happy right now," said Stricker, who rose from World No. 128 in New York to a year-end finish inside the Top 100 of the Pepperstone ATP Rankings. "I was down 3-5 and then I came back in the fourth set. I don't know how, but I did it somehow and then I kept playing very high level tennis. I am a bit speechless but it is a great day."
Photo: Sarah Stier/Getty Images