John Isner has battled his way into the third round of the Madrid Open courtesy of a 7-6(5) (11)6-7 6-1 victory over Thomaz Bellucci this afternoon.

Neither player would be moved on their own serve in the opening set, with Isner failing to take the only break point as the first went to a tie-break.

Even then, there was only one loss of serve as Isner made a crucial break before holding his own serve and going on to take the opener at the third time of asking.

It was much the same in the second set, although it was Bellucci this time who created the only break point as again the two players went to a tie-break.

It turned out to be a titanic struggle between the Brazilian and American, with Isner failing to take three match points and Bellucci squandering four set points before finally forcing a decider with a 13-11 win.

That seemed to take a lot out of Bellucci, who conceded the first breaks of the match in his opening two service games of the third set as Isner raced into a 5-0 lead.

Bellucci survived a match point on his way to pulling one game back, but it merely delayed the inevitable as Isner served out the set to take it 6-1.

Isner will face either Roger Federer or Nick Kyrgios in the next round.