John Isner was forced into a five-round battle with David Nalbandian before sealing a 4-6 6-3 2-6 7-6 10-8 victory.
The American got off to a slow start, losing the first set to 87th-ranked Nalbandian.
Isner fought back in the second, before again dropping the third set.
The fourth set ended in a tense tie-break, which the 16th seed took to force a fifth.
The final set went with serve, with games tied at five apiece going into the fourth hour of the match, but Isner managed to edge the contest and reach the third round after a thrilling final set.