Juan Martin del Potro caused a huge shock in the quarterfinals of the US Open as he ousted title favorite Roger Federer in a four-set thriller, returning to the semifinals for the first time since his triumph in 2009. It was an unexpected victory considering the Argentinian was battling an illness which almost forced him to retire against Dominic Thiem in the fourth round, but nonetheless, nothing could stop the fire in him as del Potro eventually claimed the win after two hours and 50 minutes of intense fighting between both players.

Pre-match analysis

Federer came into the match with his best performances of the week having defeated both Feliciano Lopez and Philipp Kohlschreiber in straight sets, a huge contrast to his five-setters which given all his fans a huge scare in the opening two rounds. The win here would send the Swiss into the semifinals for a meeting with arch rival Rafael Nadal, and the winner will take the number one ranking after the tournament. However, del Potro certainly did not read the script and spoiled the fun for the fans.

Meanwhile, del Potro entered his second consecutive US Open quarterfinal, having fallen to eventual champion Stan Wawrinka last year, with two impressive victories in previous rounds. Defeating 11th seed Roberto Bautista Agut in straight sets and coming from 1-6 2-6 down against sixth seed Dominic Thiem, saving two match points in the process, del Potro battled his sickness and powered to a dramatic victory.

Juan Martin del Potro applauds the crowd | Photo: Abbie Parr/Getty Images North America
Juan Martin del Potro applauds the crowd | Photo: Abbie Parr/Getty Images North America

Del Potro clinches the first break at the eleventh hour and seals the first set

Both players made a solid start on their serves with neither able to make a breakthrough on the return, but Federer had a shaky game early on as the Argentinian managed to get to deuce. However, the Swiss maestro held on to remain on serve. It was a string of ten consecutive service holds, which almost did not live up to the hype this encounter received, but the first break point of the match finally surfaced in the 11th game when Federer threw in an unexpected double fault, his first of the match, to gift del Potro a break point.

The 2009 champion then produced an unbelievable forehand passing winner to convert it, taking the lead for the first time in the match. Not disappointing his fans, the Argentinian comfortably served out the first set 7-5 after just 41 minutes of play.

Juan Martin del Potro celebrates winning a point | Photo: Al Bello/Getty Images North America
Juan Martin del Potro celebrates winning a point | Photo: Al Bello/Getty Images North America

Federer strolls to level the match

Keeping the momentum running in him, del Potro got to deuce in the opening game of the second set but Federer was able to find his best first serves to come back from the brink and narrowly hold his serve. The Australian Open champion then earned his first break point of the match but was unable to pounce on his opponent’s second serve as del Potro came up with a powerful forehand winner at the net which eventually paved his path to clinching the service hold.

However, that break point proved to be a premonition of what was going to happen next as the Swiss rattled off the next three games within a blink of an eye, breaking serve to love along the way. Without facing any problems, Federer eventually served out the second set 6-3 to level the scores.

Roger Federer celebrates winning the point | Photo: Clive Brunskill/Getty Images North America
Roger Federer celebrates winning the point | Photo: Clive Brunskill/Getty Images North America

Federer wastes four set points and del Potro comes back from the brink to take the lead

Del Potro made a booming start to the third set as unforced errors proved to be costly for Federer, who eventually double-faulted on break point in the second game as he gifted del Potro with the break in the early stages. The Argentinian then easily consolidated the break for a 3-0 lead before earning yet another break point in the fourth game, looking to stroll through this set. Nonetheless, Federer remained composed and narrowly held his serve to get on the scoreboard in the third set. The Swiss made an unexpected fight back from being 1-4 down as del Potro returned the favor, double-faulting on break point to return on serve.

The set eventually proceeded to a tiebreak to decide the winner. With some impressive play, Federer earned two set points when leading 6-4 after a tussle. He earned a total of four set points but del Potro made a screaming forehand return which was just on the line to save one of them before serving an unreturnable serve to return level.

Roger Federer hits a backhand slice | Photo: Clive Brunskill/Getty Images North America
Roger Federer hits a backhand slice | Photo: Clive Brunskill/Getty Images North America

Unexpectedly, he lost the third with a backhand mishit at the net, a shot where he could have easily put off for a 2-1 lead. The fourth was saved by a big forehand winner before del Potro finally earned one of his. Yet another volley winner completed the incredible comeback by the 2009 champion, allowing him to regain the lead having saved four set points.

Del Potro seals the huge upset

After a tight start to the fourth set which saw the returner only winning one solitary point in the first four games, it was del Potro who once again drew the first blood and made the first breakthrough in the fifth game. Federer had previous saved two break points with some clutch aggressive play, before sending a smash directly into the net and allowing del Potro to earn his third break point.

He was finally third-time lucky as he managed to send an incredible backhand return winner off a 121 mph first serve, putting himself in an advantageous position to take the huge win. Federer remained all over the place on the return and soon found himself serving to stay in the match at 3-5 down.

Roger Federer in action | Photo: Clive Brunskill/Getty Images North America
Roger Federer in action | Photo: Clive Brunskill/Getty Images North America

Pressure and the noise from the crowd seemed to have gotten to him as he was 3-5 0-30 down, two points away from defeat. Nonetheless, his years of experience got him through the narrow service game and forced del Potro to serve the match out. One would expect del Potro to falter when facing the pressure, and he almost did after allowing Federer to get to 30-30 despite being 30-0 up.

With the golden opportunity to earn break point right at the brink, Federer could have put off an easy volley winner but instead, he sent it to the stands as he gifted del Potro with his first match point. With a powerful 130 mph serve followed by yet another strong forehand, the Argentinian successfully served out the huge upset after two hours and 50 minutes of thrilling tennis.

Respect: Roger Federer congratulates del Potro on the win | Photo: Clive Brunskill/Getty Images North America
Respect: Roger Federer congratulates del Potro on the win | Photo: Clive Brunskill/Getty Images North America

Stats Corner: del Potro was more consistent and solid

Both players were incredibly solid on their serves throughout the whole match, but it was del Potro who was better at the crucial moments. Federer won 73 percent of his first service points before claiming 57 of points behind his second delivery. The winner of the match performed much better on his powerful first serves, winning 81 percent of points off them. His second serves were a little shaky but it still got him through despite only a mere 51 percent of points being won.

Federer charged towards the net for an incredible 53 times throughout the whole match but was less effective than usual there as he was too leaky, losing 36 percent of his net points. Although both players had a positive winner-unforced error ratio, Federer’s unforced errors proved to be more costly, especially with his errors on his set points in the third set and at 4-5 30-30 in the fourth. Del Potro won just six more points than his opponent throughout the match, showing how tight this match was.

Juan Martin del Potro hits a forehand | Photo: Al Bello/Getty Images North America
Juan Martin del Potro hits a forehand | Photo: Al Bello/Getty Images North America

Next up: Top-ranked Rafael Nadal looms in the semifinals

Juan Martin del Potro will now face the world number one Rafael Nadal in the semifinals two days later, with the winner earning a place in the final. Nadal leads their head-to-head 8-5 but it was the Argentinian who won their last two meetings and their last encounter at Flushing Meadows, which ended in a one-sided 6-2, 6-2, 6-2 scoreline for del Potro back in 2009 when he was the eventual champion.