NEW YORK, United States, September 9, 2026: Alexander Blockx had already spent two days trying to outrun a rib problem that nearly ended his US Open before the quarterfinals. Against Karen Khachanov, the body finally stopped giving him somewhere to hide.
Khachanov advanced to the US Open semifinals after Blockx was unable to continue with the score at 6-2, 7-5, 3-2 inside Arthur Ashe Stadium, ending the Belgian’s remarkable breakthrough run in painful fashion.
The retirement did not rescue Khachanov from a difficult position. He was already firmly in control.
The 30-year-old won the opening set 6-2, edged the second 7-5 and had moved ahead 3-2 in the third when Blockx stopped. Khachanov finished with 80 points won to Blockx’s 60, converted four of six break points and did not face a single break point himself.
That matters because the result should not be reduced to the injury alone.
Blockx’s physical condition shaped the match, but Khachanov had spent more than two sets making sure the Belgian never found the kind of rhythm that had carried him through the first week. The Russian now returns to the US Open semifinals for the first time since 2022 and awaits the winner of Alexander Zverev against Botic van de Zandschulp.
For readers following the tournament from the opening rounds, The Sports Encounter’s US Open 2026 preview remains the main guide to the draw, contenders and major storylines in New York.
Khachanov vs Blockx: Quarterfinal at a Glance
| Statistic | Karen Khachanov | Alexander Blockx |
|---|---|---|
| Result | Advanced | Retired |
| Score when match ended | 6-2, 7-5, 3-2 | 2-6, 5-7, 2-3 |
| Aces | 6 | 8 |
| Double faults | 2 | 4 |
| First serve in | 59% | 64% |
| First-serve points won | 87% | 66% |
| Second-serve points won | 68% | 61% |
| Break points | 4/6 | 0/2 |
| Receiving points won | 29 | 15 |
| Total points won | 80 | 60 |
| Games won | 16 | 9 |
Khachanov Took Control Before the Injury Ended It
The scoreboard tells an important part of the story.
Khachanov did not stumble into the semifinal because Blockx stopped.
He had already won 16 games to nine.
He had taken 80 total points compared with Blockx’s 60.
Most tellingly, Khachanov won 87% of points behind his first serve and 68% behind his second. Blockx never managed to establish sustained pressure on return.
The Belgian did not convert a break point because he never earned one according to the final match statistics displayed after play ended.
Khachanov, by contrast, converted four of six.
That gap explains why a match featuring only moderate differences in ace count and first-serve percentage still felt one-sided for long periods.
Blockx Entered the Match With a Warning Sign
The physical problem was not new.
Blockx had suffered a rib injury during his fourth-round victory over Francisco Cerundolo and admitted afterward that he had come close to retiring from that match.
The official US Open quarterfinal preview specifically identified recovery as his biggest challenge before facing Khachanov.
Blockx had required treatment during the Cerundolo match and later said the pain had become sharp enough that stopping had been a real possibility.
He survived that afternoon.
Two days later, the same physical concern hung over his first Grand Slam quarterfinal from the moment he walked onto Arthur Ashe Stadium.
The First Set Established Khachanov’s Advantage
Khachanov won the opening set 6-2 and immediately forced Blockx into a different kind of match from the ones that had powered his breakthrough.
The Belgian had built much of his US Open success around serving aggressively, shortening points and protecting himself when rallies became uncomfortable.
Against Khachanov, that formula never settled.
Blockx still produced eight aces across the match, two more than his opponent, but first-strike success did not translate into control of his service games.
Khachanov repeatedly made enough returns to force another shot.
Once the rallies extended, Blockx had to manage both the Russian’s weight of shot and the physical limitations he had carried into the match.
That was an increasingly difficult combination.
The Second Set Was Blockx’s Last Real Opening
The 7-5 second set was much more competitive.
Blockx held closer to Khachanov and gave himself a chance to reach a tiebreak, which could have changed the emotional shape of the quarterfinal.
Khachanov denied him that opportunity.
Breaking late for the set gave the Russian a two-set advantage and removed almost all margin for error from a player already dealing with physical uncertainty.
That moment was crucial because Blockx no longer had the option of conserving energy and hoping to steal one set.
He now needed three.
Against a player who had lost only nine games and had not surrendered serve, that became an enormous demand.
Blockx’s Numbers Show Where the Match Slipped Away
The most revealing statistical difference came on first serve.
Blockx landed 64% of his first deliveries, better than Khachanov’s 59%.
Khachanov still won 87% of his first-serve points.
Blockx won 66%.
That 21-point percentage gap is huge in a match where both players were getting a reasonable number of first serves in.
The Russian was also more secure behind his second delivery, winning 68% compared with Blockx’s 61%.
Khachanov therefore had an advantage on both versions of the serve battle.
That allowed him to play return games with more freedom because his own service games were rarely becoming stressful.
Blockx’s Run Still Changed Belgian Tennis History
The ending should not erase what came before it.
Blockx arrived in New York playing the first US Open main draw of his career.
He left as the first Belgian man ever to reach the US Open quarterfinals.
The 21-year-old defeated Francisco Cerundolo 6-3, 4-6, 7-5, 7-5 in the fourth round after previously producing one of the tournament’s major upsets against Flavio Cobolli.
The official US Open report on his win over Cerundolo noted that Blockx became the first Belgian man to reach the quarterfinals in tournament history.
He also became the youngest Belgian man ever seeded at a Grand Slam and climbed dramatically through the rankings during a season that began with him outside the Top 100.
This was not a lucky week.
It was a breakthrough.
Khachanov Has Rebuilt His Tournament From Almost Nothing
Khachanov’s route to the semifinals is nearly as interesting.
He arrived at the US Open on a four-match losing streak and without a victory during the North American hard-court swing.
That form did not suggest a deep run.
New York changed it.
Khachanov defeated No. 3 seed Felix Auger-Aliassime earlier in the tournament and then survived a five-set battle against Learner Tien in the fourth round.
The US Open’s official report described the 7-5, 4-6, 6-7(6), 6-1, 6-4 victory over Tien as Khachanov’s seventh career Grand Slam quarterfinal qualification.
Now he has gone one round further.
That puts him back in the US Open semifinals four years after his previous appearance in the last four in 2022.
Experience Became More Important as Blockx Faded
Khachanov’s advantage was not simply physical.
He knew this stage.
Blockx did not.
The Russian had already reached Grand Slam semifinals at the US Open and Australian Open before Wednesday. He had also made major quarterfinals across all four Slams.
Blockx was playing his first major quarterfinal.
That contrast becomes especially relevant when one player is carrying an injury.
Khachanov did not give Blockx easy service games or low-pressure stretches in which to manage the body.
He made the Belgian keep playing points.
That sounds simple.
It is often exactly what experienced players do against compromised opponents.
The Men’s Draw Is Opening in Unexpected Ways
Khachanov’s semifinal place adds another surprise to a men’s tournament that entered New York without the usual certainty.
Jannik Sinner did not play because of a knee injury.
Carlos Alcaraz was eliminated by Ben Shelton after a five-set match that ended at 3:33 a.m., one of the defining contests of the tournament. The Sports Encounter’s report on Shelton’s victory over Alcaraz examined how the American survived one of the most demanding matches of his career.
Frances Tiafoe has also reached the semifinals after coming back from two sets down against Alex Michelsen.
The last four therefore already contain names and routes that few would have predicted before the tournament.
Khachanov now joins that picture.
Zverev or Van de Zandschulp Comes Next
Khachanov will face the winner of the remaining quarterfinal between top seed Alexander Zverev and Botic van de Zandschulp.
Zverev entered the quarterfinals as the strongest-ranked player left in this half of the draw and has already won the 2026 French Open.
Van de Zandschulp has taken a very different route.
The Dutchman survived a five-hour, 13-minute match against Arthur Gea to reach the last eight, adding another physical variable to a tournament already shaped by endurance.
The Sports Encounter’s US Open 2026 coverage will follow that quarterfinal and what it means for Khachanov’s semifinal matchup.
Gauff, Rybakina and the Women’s Draw Add to a Chaotic New York
The men are not the only ones producing dramatic quarterfinals.
Coco Gauff came from a set down to beat Mirra Andreeva in three sets, winning 2-6, 7-6(7), 6-2. The Sports Encounter’s analysis of Gauff’s comeback showed how the second-set tiebreak changed the entire match.
Elena Rybakina also advanced after defeating Zheng Qinwen and secured the world No. 1 ranking in the process. Rybakina’s victory set up one of the tournament’s strongest semifinal matchups against Gauff.
Jessica Pegula is already through on the other side after beating Emma Navarro.
The final days in New York are therefore becoming less predictable rather than more.
The Sports Encounter Verdict
Alexander Blockx’s quarterfinal will be remembered for the way it ended.
That is understandable.
It should also be remembered for what Khachanov had already done before the retirement.
He had won the first two sets.
He had taken 20 more points.
He had broken four times.
He had not been broken once.
The rib issue may have taken away the finish the match deserved, but it did not invent Khachanov’s advantage.
For Blockx, the disappointment will eventually sit beside a much larger achievement. At 21, in his first US Open main draw, he became the first Belgian man to reach the quarterfinals in New York and proved he could beat established players on one of tennis’ biggest stages.
For Khachanov, the opportunity is immediate.
He arrived at Flushing Meadows without form.
He is leaving the quarterfinals one victory away from a Grand Slam final.
Follow The Sports Encounter’s tennis coverage and our US Open 2026 hub for the remaining quarterfinal, semifinal previews and continuing coverage from New York.