Juan Martin del Potro has conceded that he did not know too much about Rhyne Williams prior to their meeting at the Australian Open earlier today.

Williams, 22, had been rated as a rank outsider for the clash, but he looked to be on his way to causing an upset when he claimed the first set on a tie-break.

However, Del Potro rallied to win the next three sets, thus booking his place in the second round of the Grand Slam.

"I didn't expect this kind of match against him. I didn't know too much before the match about how he plays tennis, but he served well," he told reporters.

"His forehand is good. I started the match really, really slow, and then it was difficult to come back and play my game. In the end, I served well and I hit some good forehands.

Del Potro will now take on Spain's Roberto Bautista Agut for a place in the third round.