Both sets were decided with a break in the last game of the set, and the world no.11 Isner could well move for the first time in his career into the Top 10.
Isner will now play the winner of the match between the Australian qualifier Matthew Ebden and American no.8 seed Fish.
Gilles Simon of France also joined Isner in round 4 as he beat the Swiss Stanislas Wawrinka in straight sets 6-4 6-4.
Wawrinka couldn’t quite produce his game that we are normally used to, he had to ask for medical timeout in the second set. But there were just too many unforced errors from the Swiss, 52 altogether.
Simon did well to to take his chances, and although his percentage of converted break points wasn’t that high (3 out of 13), it proved to be enough to win the match in two sets.
In the next round, the French will play either Guillermo Garcia-Lopez or Ryan Harrison. Garcia-Lopez was the one to defeat world no.4 Murray in the second round.