Isner stuns Del Potro to reach Miami final

Isner returns a shot to Juan Martin Del Potro of Argentina.
Isner returns a shot to Juan Martin Del Potro of Argentina.PHOTO: AFP

MIAMI (AFP) - John Isner produced a blistering Miami Open semi-final display against crowd favourite Juan Martin del Potro to win 6-1, 7-6 (7/2) and snap the former US Open champion's 15-match winning streak.

It was a phenomenal effort from the American who blasted down 13 aces and took just one hour and 23 minutes to floor Argentina's Del Potro and book his place in Sunday's final.

Isner will meet either Alexander Zverev or Pablo Carreno Busta who play their last four match later on Friday (March 30).

Isner, 32, arrived in South Florida with just six wins to his name in 2018 but has improved with every match in Key Biscayne and is now eyeing his first ATP Masters title.

"I have played a lot of big matches and not been able to get such a good start but I am playing some of the best tennis I have played in such a long time," Isner said.

"I am so happy. He is so tired and has played so many games and although the first set was quick I knew it wouldn't be like that in the second.

"I didn't think I could turn it around like this after the year I have had so far. I started the tournament well and I have improved with every game.

"I am super fresh and ready to go for the final."

Isner, who won an impressive 83% of points on his second serve, was aiming to reach his fifth ATP Masters final and, finally, emerge victorious from one after four defeats.

The American had never reached the showpiece here but knew that with the fit again del Potro in such devastating form and unbeaten in his last 15 matches, it would take a monumental effort to upset the Argentine and his hordes of followers at Crandon Park.

The American wasted no time in breaking del Potro and racing into a 3-0 lead while sending down five aces on his own serve to brilliantly wrap up the first set in just 27 minutes.

The second set was a tight, emotional affair, going into the ninth game with the match delicately poised at 4-4.

Isner suddenly had a chance to break which was saved by del Potro after the world number 17 hit the net, a mistake which was punished by an ace and drop shot from the crowd favourite.

Deafening chants of "Delpo Delpo" rang around the main stadium here as the 29-year-old tried to force a deciding set yet Isner's serve held firm to force a tie-break.

The momentum was with the American, his serve reaching 136 mph as he flew into a 3-0 lead.

Isner's serve was relentless and on target every single time making it impossible for Del Potro to get a foothold in the game, and when an excellent passing shot gave Isner four match points, he took the first with a brilliant drop volley to complete one of the finest wins of his career.