Images from the US Open men's singles second round matches, at Flushing Meadows, New York, on Thursday.

Alcaraz dumped out in 2nd round

Former champion Carlos Alcaraz's Grand Slam winning streak came to a screeching halt at the US Open on Thursday as the Spaniard was beaten 6-1, 7-5, 6-4 by unseeded Dutchman Botic van de Zandschulp in the second round.

Alcaraz never recovered from a shaky start and made unforced errors throughout as Van de Zandschulp ended the French Open and Wimbledon champion's 15-match winning run at the majors.

The 21-year-old was on the back foot early on as Van de Zandschulp claimed the opening three games with some resolute defending from the back of the court, and the Dutchman broke again in the sixth game en route to taking the first set.

Alcaraz produced a stunning forehand pass to hold serve in the first game of the next set but the four-times major winner's struggles to close out points resurfaced as Van de Zandschulp broke for a 2-1 lead.

A tactical tweak to return serve from deeper helped Alcaraz break back immediately but the 2022 champion gifted his opponent another break with a double fault and Van de Zandschulp went on to comfortably double his advantage in the match.

After briefly leaving the court before the third set, Alcaraz found himself in deeper trouble after a wayward forehand handed Van de Zandschulp a break.

He hit back immediately and found his smile again, but world number 74 Van de Zandschulp got his nose in front and completed a stunning upset on serve.

"Actually I am a little bit lost for words. It's been an incredible evening here," said Van de Zandschulp. "I think from point one here today I believed (I had) a chance.

"I had some nerves but I think if you want to beat one of these guys you have to be unbelievably calm and keep your head there."

Medvedev powers through to 3rd round

Former champion Daniil Medvedev was far from his best but still did enough to dispatch Hungary's Fabian Marozsan 6-3, 6-2, 7-6(5) on Thursday to reach the US Open third round.

Medvedev won an opening set that included six breaks of serve across nine games, with the Hungarian's serve failing to pack a punch and the Russian's uncharacteristically tentative serving leading to four double faults.

Medvedev was far more comfortable from there, helped by his opponent's 45 unforced errors and catalogue of poorly-timed drop shots.

Medvedev sealed victory with a leaping backhand on match point and afterwards appeared annoyed with the muted reaction from the stands at Flushing Meadows, where he has had a rocky relationship with the crowds over the years.

Despite making the Australian Open and Indian Wells finals this year, fifth seed Medvedev was not among the favourites coming into the U.S. Open after first-round exits at tune-up events in Canada and Cincinnati.

Medvedev, who was broken four times in the match, faces Italian 31st seed Flavio Cobolli in the third round on Saturday.

Sinner breezes past Michelsen

Earlier, top seed Jannik Sinner beat American Alex Michelsen 6-4, 6-0, 6-2 to reach the third round of the US Open, where the Italian's doping case remains a focus even though he was cleared of wrongdoing.

Sinner converted eight of his 16 break-point chances en route to dispatching Michelsen in 99 minutes on Arthur Ashe Stadium.

In the early goings Michelsen proved up for the challenge as he twice came back from a break down in the first set, but when Sinner broke a third time for a 5-4 lead he promptly closed out the tighly-contested frame on serve.

Sinner found another gear in the second set and had a much easier time as he raced out to a 3-0 double-break lead to seize control and never looked back as Michelsen's serve suddenly abandoned him.

Michelsen made an encouraging start to the third set but Sinner remained all business and continued applying pressure, eventually earning the decisive break for a 3-2 lead and going on to serve out the match with a routine hold.

The victory was in stark contrast when compared to their first meeting two weeks ago during the second round of a US Open tune-up event in Cincinnati where Sinner prevailed in two close sets en route to lifting the title.

Up next for Sinner, who counts the Australian Open among his ATP Tour-leading five titles this year, will be either Italy's Mattia Bellucci or Australia's Christopher O'Connell.

Ahead of the year's final Grand Slam, the International Tennis Integrity Agency revealed that Sinner had tested positive twice for an anabolic agent in March but avoided a ban as it was ruled he bore no fault or negligence for the violations.

De Minaur survives first-set fright against unseeded Virtanen 

Australia's 10th seed Alex de Minaur overcame a potential banana skin to beat Finland's big-hitting Otto Virtanen 7-5, 6-1, 7-6(3) on Grandstand to move into the third round.

De Minaur is playing in his first tournament after pulling out of Wimbledon with a hip injury, with the 25-year-old also withdrawing from the singles at the Paris Olympics. He was also an injury doubt for the second round match against Virtanen.

But after an early scare when he was serving to stay in the set, he recovered quickly to dismantle his Finnish opponent who was looking to reach the third round at a Grand Slam for the first time in his career.

"I'm happy to keep going every day, I'm getting a little bit better and I'm looking forward to what's to come," De Minaur said.

"Still not a lot of expectations, but I know every time I step out there I'm going to compete, I'm going to try my hardest and hopefully put on a show."

De Minaur had never faced Virtanen before and the Australian found himself 3-0 down at Grandstand in the blink of an eye when the towering Finn looked formidable on serve while also confidently approaching the net.

Although ranked 125 in the world, Virtanen looked like a seasoned professional and was soon 5-2 up, but that was just the wake-up call De Minaur needed as the Australian reeled off seven consecutive games to take the set and go 2-0 up in the second.

Having looked well set to spring an upset, Virtanen was suddenly his own worst enemy as his unforced error count started to pile up. The 23-year-old also took a medical timeout to receive treatment on his back.

The physio's efforts did not yield the desired results for Virtanen who lost his intensity and could not challenge De Minaur in the longer rallies as the 10th seed cruised into a two-set lead.

At this point, Virtanen was going for broke on most of his shots without looking at his error count and he managed to engineer a mini-recovery in the third set as he kept pace with De Minaur.

Virtanen forced a tiebreak but neither he nor his coach had answers when a clinical De Minaur raced into a 4-0 lead before clinching victory on his fourth match point when the Finn found the net.

Machac takes down 16th seed Korda 

Sebastian Korda's hopes of reaching the third-round at the US Open for the first time fell short as the 16th seed struggled to hold serve against the Czech Republic's mixed doubles Olympic gold medalist Tomas Machac and was beaten 6-4, 6-2, 6-4.

Machac, adding to third round spots at both the Australian Open and Roland Garros in 2024, continued to build his major habits off the back of 31 winners in the two-hour triumph.

A backhand pick up followed by a forehand pass set the tone for a strong start from recent Washington champion Korda. On two occasions, the towering American spun 360 degrees mid-point and managed to connect with a passing winner. Those were the highlights to fire the 24-year-old a break ahead.

Machac found himself 2-4, 0-40 down, but managed to click into an unplayable gear off the forehand wing in particular. Dragging Korda side-to-side, the world No. 39 pulled the trigger on a brace of bullet forehands to erase the deficit. Four games on the trot and the Czech proved he was up to task for an upset.

Korda was visibly struggling physically and had a medical timeout for treatment on his right arm. The serve was the obvious stroke giving Korda the most grief, as Machac pounced for an instant break.

The No. 16 seed conjured up a couple of sublime points with a carved backhand slice and lasered backhand, but Machac was motoring two sets up with clean and slick tennis. There was no reaction from Machac, striding to the sit-down, just like his tennis, with real purpose.

The No. 16 seed valiantly battled on and called "come on" following a forehand arching onto the baseline. Some more vicious slice and an instinctive backhand gained a 3-0 lead for Korda, despite his arm still causing pain and an untimely distraction.

Once again, Machac battled back from 2-4. A Michael Jordan fan, the world No. 39 leapt into the air for a mid-flight forehand cross court en route to grinding down the American and securing a statement win in straight sets.