Good evening, and welcome to our LIVE coverage of Juan Martin del Potro v John Isner.

That was a bit of an epic match, and not always in a good way.

Del Potro will face the winner of today's next men's singles match - Rafael Nadal or Dominic Thiem.

Del Potro tells the New York crowd that the US Open is his favourite tournament.

DEL POTRO 6-7(5) 6-3 7-6(4) 6-2 ISNER: There's a nice hug between the pair at the net as Isner nets his last shot, and Del Potro allows that famous beam to cross his face after three and a half hours of gruelling tennis.

DEL POTRO 6-7(5) 6-3 7-6(4) 5-2 ISNER: Delpo is raring to get back to his seat, ready for the massage from the trainer.

DEL POTRO 6-7(5) 6-3 7-6(4) 4-2 ISNER: Isner noted that problem with Delpo's leg and is going to try and make him move.

Del Potro seems to have some stiffness in his left leg.

DEL POTRO 6-7(5) 6-3 7-6(4) 4-1 ISNER: Isner has a break point here and then lashes his return much to his massive frustration.

DEL POTRO 6-7(5) 6-3 7-6(4) 3-1 ISNER: Gritty from Isner, who looks exhausted but is summoning up his last reserves.

DEL POTRO 6-7(5) 6-3 7-6(4) 3-0 ISNER: And then a straightforward hold of serve for Del Potro who's looking much more composed now.

DEL POTRO 6-7(5) 6-3 7-6(4) 2-0 ISNER: There's the break! Del Potro is crushing the return backhand.

DEL POTRO 6-7(5) 6-3 7-6(4) 1-0 ISNER: That's the start to the fourth set the Argentinian wanted!

Isner opts to invoke the ten-minute heat break, unsurprisingly. Time for some air-conditioning.

DEL POTRO 6-7(5) 6-3 7-6(4) ISNER: Isner shouts at his racquet after he fails to return a Del Potro mishit, and then the third seed steps it up on serve. Another mini-break follows before he serves out the set.

DEL POTRO 6-7(5) 6-3 6-6 ISNER: Another tie-break, then? Yes.

DEL POTRO 6-7(5) 6-3 5-6 ISNER: Isner isn't happy with Delpo's rowdy friends in the stands, and that fires him up a touch more.

DEL POTRO 6-7(5) 6-3 5-5 ISNER: Hold to love for Delpo, and Isner breathes deeply as he prepares for his own service.

DEL POTRO 6-7(5) 6-3 4-4 ISNER: Del Potro allows the power of Isner to blister past him and prepares for his serve.

DEL POTRO 6-7(5) 6-3 4-4 ISNER: Hold to love for Del Potro.