Pablo Carreno Busta holds his nerve against Diego Schwartzman to reach US Open semi-finals for the first time

The World No 13 had never gone beyond the third round of a Grand Slam event before this summer, but is now just two matches away from winning the US Open

The 26-year-old has a shot of making the US Open final (Getty)

In this most open of Grand Slam tournaments it felt appropriate that the first man into the semi-finals was a player who would barely be recognised by tennis fans outside his own country. Pablo Carreno Busta had never gone beyond the third round of a Grand Slam event before this summer, but the 26-year-old Spaniard is through to the semi-finals of the US Open after beating Argentina’s Diego Schwartzman 6-4, 6-4, 6-2.

Carreno Busta had been left as the highest ranked player in the bottom half of the draw after Andy Murray’s withdrawal and the early exits of Alexander Zverev, Marin Cilic and Jo-Wilfried Tsonga. The world No 19 has taken his chance with both hands by reaching the last four without dropping a set.

The way in which the bottom half of the draw here has opened up over the last 10 days is underlined by Carreno Busta’s progress through the competition.

He became the first player in Grand Slam history to face four qualifiers in a single tournament as he beat Evan King (world No 308), Cameron Norrie (No 225), Nicolas Mahut (No 115) and Denis Shapovalov (No 69) in his first four matches. Schwartzman, the world No 33, was the highest ranked player he has faced so far.

Schwartzman, who stands just 5ft 7in tall, was the shortest male quarter-finalist at a Grand Slam tournament since Jaime Yzaga, who was the same height, played here 23 years ago. The 25-year-old Argentinian reached the third round of a Grand Slam competition for the first time at this year’s French Open and bettered that run here with victories over Carlos Berlocq, Janko Tipsarevic, Cilic and Lucas Pouille.

The world No 33 might have gone even further but for the fact that against Carreno Busta he played so many of the big points poorly. Schwartzman, who packs a big punch for a player of his stature, frequently worked his way into positions of strength but all too often failed to capitalise on his chances. The Argentinian took only two of his 10 break points, while Carreno Busta converted six of his eight.

Schwartzman was unable to extend his fine run (Getty)

Schwartzman got off to a poor start as he was broken to love in the opening game and to 15 six games later. Carreno Busta double-faulted on break point when he served for the set at 5-2 but made no mistake two games later.

The Spaniard also struck early in the second set, breaking to love in the third game, only for Schwartzman to break back immediately, cracking a big forehand winner on his second break point.

Schwartzman was working his way back into contention, but the set and the match took a decisive turn when Carreno Busta served at 3-4 and 0-40. Schwartzman failed to take any of his break points and was left to rue in particular a woeful forehand which he put into the net on the second of them.

Carreno Busta was simply too good for his opponent (Getty)

In the following game the Argentinian went 15-40 down, upon which Carreno Busta made a bold net approach and put away a forehand volley. The Spaniard went 15-30 down when he served for the set but then hit two successive aces before converting his second break point with a service winner.

Carreno Busta broke in the opening game of the third set and again in the seventh before serving out for victory after just an hour and 58 minutes, completing the job when Schwartzman shanked a backhand. The Spaniard will next meet the winner of Tuesday’s later quarter-final between Sam Querrey and Kevin Anderson.

“It’s something that I always dreamed of but which I never thought would happen here,” Carreno Busta said when asked how it felt to be through to the semi-finals. “I tried to be focused all the time. Diego is a fighter. You need to be focused, play aggressive and try to dominate the points. If you don’t, Diego will beat you for sure.”

The Spaniard has never before reached the semi-finals of a Slam (Getty)

Carreno Busta reached the doubles final here last year and said that playing doubles helps his singles game. “It’s very good because it helps you to practise your serve, your volleys, playing at the net, being aggressive,” he said. “The final here last year was my first match in Arthur Ashe Stadium and that experience helped me this year.”

Wednesday’s quarter-finals will see Roger Federer and Rafael Nadal attempt to set up their long-awaited semi-final showdown here. Federer appears to have the more difficult task as he takes on Juan Martin del Potro following the Argentinian’s remarkable comeback from two sets down to beat Austria’s Dominic Thiem, while Nadal faces the 19-year-old Russian, Andrey Rublev.

Federer and Nadal had played each other 37 times but never here. They have met five times at the French Open, four times at the Australian Open and three times at Wimbledon. Nadal leads their head-to-head record 23-14.

Jamie Murray and his Brazilian partner, Bruno Soares, went out in the quarter-finals of the doubles, losing 6-1, 6-2 to the Dutchman Jean-Julien Rojer and the Romanian Horia Tecau in just 62 minutes. Murray and Soares, who were the defending champions, never recovered after losing the first four games.