Alexander Blockx Is No Longer Waiting His Turn

Alexander Blockx began 2026 outside the world’s top 100 and needing to qualify for the Australian Open. Eight months later, the 21-year-old Belgian is a US Open quarter-finalist, a Masters 1000 semi-finalist and one of the most convincing examples yet that the next generation of men’s tennis is arriving as a group rather than one at a time.

Blockx reached the last eight at Flushing Meadows by defeating Francisco Cerúndolo 6-3, 4-6, 7-5, 7-5 in three hours and 15 minutes on Arthur Ashe Stadium. It was his second victory over the Argentine this season, his fourth win of an extraordinary US Open debut and he also grabbed a piece of Belgian tennis history: no Belgian man had previously reached the singles quarter-finals in New York.

But dig a little deeper, and the result on the surface doesn’t tell the whole story. Blockx began experiencing a sharp pain in his rib during the second game and required treatment during the match.

“From the second game I started feeling really sharp in my rib,” he said afterwards.

Cerúndolo had opportunities to take advantage, particularly during a first set that was much closer than its score suggested. Blockx nevertheless found a way to keep points short enough, protect his serve under pressure and remain competitive until the treatment began to help.

“I was just holding on to be honest,” Blockx said. “Even though I won that first set 6-3, it could have been the other way round.”

Cerúndolo responded by taking the second set 6-4, but the match turned late in the third. Serving at 5-5, Blockx fell behind 0-40. Three break points offered Cerúndolo the chance to serve for a two-sets-to-one advantage. Blockx erased all three, using the first-strike power that is fast becoming a trademark for him, held for 6-5 and then broke to steal the set.

The fourth was similarly tight. Neither man could create separation until Cerúndolo served at 5-6. Blockx applied one final burst of return pressure, gained the decisive break and fell to the court when the Argentine’s last shot landed out.

The match statistics don’t always reveal the story, but there are a few telling numbers. Blockx served 10 aces to Cerúndolo’s five and won 57 of 77 first-serve points, a success rate of 74 per cent. He also won 29 of 54 points behind his second serve. Most importantly, he converted six of 12 break points while Cerúndolo managed only three conversions from 17 opportunities. Blockx saved 14 break points in all, including the three that threatened to decide the third set.

It was a performance built on repeatedly winning the right point, rather than a full match domination. The Belgian made only 56 per cent of his first serves and committed seven double faults and was far from flawless, but his willingness to trust the serve in the important moments was decisive. Cerúndolo won 57 of 79 first-serve points and generated more break opportunities; Blockx was simply better when those opportunities became bigger.

Blockx had never previously played a competitive match on the 23,200-seat stage that is Arthur Ashe. He walked onto it that morning for his warm-up and described the experience as “unreal”. Winning there, he said, was “even crazier”.

Blockx opened his US Open campaign by defeating qualifier Tomás Barrios Vera 6-3, 6-4, 6-2, then beat veteran Marco Trungelliti 6-3, 6-2, 3-6, 6-1. In the third round he recovered from losing the opening set to eliminate fifth seed and French Open finalist Flavio Cobolli 6-7(4), 6-3, 6-0, 6-3. Blockx struck 17 aces in that victory, completed it in two hours and 44 minutes and called the atmosphere “one of the craziest experiences so far in my career.”

Cerúndolo presented a different challenge though. The Argentine had recovered from two sets and a break down to defeat ninth seed Taylor Fritz and had already won five ATP Tour titles during his career. He also arrived with a reason for revenge: Blockx defeated him 7-6(8), 6-2 in Madrid earlier this year.

Before their New York rematch, Blockx tried to play down any previous match-up.

“Francisco is an amazing player,” he said. “We played once before. That was on clay. Now, conditions are completely different.”

The outcome, however, was the same. Blockx’s ability to beat Cerúndolo on both clay and hard court is one measure of how quickly his game has expanded.

The first major sign came in Madrid. Ranked No. 69 at the start of that tournament, Blockx defeated three consecutive top-20 opponents — Félix Auger-Aliassime, Cerúndolo and defending champion Casper Ruud — to reach his first Masters 1000 semi-final. His 6-4, 6-4 victory over Ruud made him the first Belgian man to reach the Madrid semi-finals and only the second man born in 2005 or later, after Jakub Menšík, to reach the last four of a Masters 1000 event.

Blockx’s explanation for that breakthrough sounds like it could’ve been some sort of a preview for New York.

“Once you get confident and you feel your game, a lot can happen,” he said during the Madrid run.

He is unusually calm between points for such an imposing ball-striker. In Madrid, he explained that he sometimes had songs running through his head while serving out matches.

“In those moments I’m not nervous at all,” he said.

If he can maintain that composure, it will become a competitive weapon: the bigger the score, the more willing he appears to trust his patterns. Let’s see if that remains during the pointy end of a Slam…

His progress becomes still more interesting when placed beside his peers. Blockx was born in April 2005, the same year as Menšík and Learner Tien, while João Fonseca was born in 2006. Their careers have been intertwined and compared since junior tennis.

Blockx defeated Tien 6-1, 2-6, 7-6(9) to win the 2023 Australian Open boys’ singles title, converting his third championship point to take the deciding tie-break 11-9. At the same tournament, Blockx partnered Fonseca in the boys’ doubles final; they lost 6-4, 6-4 to Tien and Cooper Williams.

They have now all become central figures in the ATP’s emerging Next Gen.

Tien reversed the Australian Open result in the 2025 Next Gen ATP Finals championship match, beating Blockx 4-3(4), 4-2, 4-1. Fonseca had won that event a year earlier, while Menšík became the first member of their birth-year group to reach a Masters 1000 semi-final. Blockx has not progressed in a straight line or collected senior trophies as quickly as some of those contemporaries, but his 2026 season has closed much of the apparent distance.

There is also an obvious comparison at this US Open. Tien, seeded 14th, reached the fourth round before losing a five-set match to Karen Khachanov—the man Blockx will now face in the quarter-finals. Blockx, seeded 28th, has gone one round further while defeating two established seeds in succession.

Alex Michelsen, born in 2004, has also reached his first major quarter-final in New York. Rather than one player separating from the field, several members of the ‘post-Alcaraz’ generation are beginning to occupy the second week of majors together.

Blockx’s ranking also reflects the acceleration of this season. He began this season at No. 117. His Canberra Challenger title in January took him into the Top 100; Madrid carried him into the Top 40. Following his fourth-round victory in New York, he has risen to No. 26 in the ATP live rankings, guaranteeing another career high when the post-US Open rankings are released.

Khachanov will provide his hardest physical examination yet. The experienced Russian reached the quarter-finals by recovering to defeat Tien 6-3, 1-6, 6-7(2), 6-3, 6-4. Blockx will enter with uncertainty around his rib and the accumulated strain of consecutive four-set matches. He will also enter with confidence, knowing that his best tennis has already beaten opponents of comparable standing.

The Belgian arrived in New York as a dangerous young seed making his tournament debut. He now walks into the quarter-finals as the first Belgian man ever to reach that stage at the US Open, one victory from a major semi-final and firmly established inside the sport’s next wave.

Read more of our exclusive feature articles here.

Read more of our player focus articles here.

Follow The Tennis Site on X: @thetennissite

Follow Todd Scoullar on X: @toddscoullar