Guido Pella stuns John Isner in Rio Open marathon

Unseeded Argentinian Pella surprisingly made it through to the second round thanks to a hard-fought 7-6 (7-5) 5-7 7-6 (10-8) win on the clay courts in Rio de Janeiro.

The three-hour battle at the ATP 500 tournament was the only first-round match to take place on Monday after rain forced Alexandr Dolgopolov's showdown with eighth seed Thomaz Bellucci to be postponed.

But fans in Brazil did not leave disappointed as Pella and big-serving Isner played out a thriller.

Isner fired down 31 aces and won 83 per cent of his first serves but he only converted one of 11 break-point opportunities against Pella, who closed out the match with a stunning left-hand forehand down the line.

Pella, who fended off 10 of 11 breaks, will face the winner of Santiago Giraldo and Gastao Elias in the next round.