The meeting spanned ten minutes under four hours as del Potro relinquished only one break of serve to the 21-year-old. The pair met at the ASB Classic last week with little to separate them and it was a similar theme on a packed Hisense Arena.
A mouthwatering third round meeting with Tomas Berdych awaits on Saturday after the 19th seed dispatched Guillermo Garcia-Lopez in four sets.
Temperatures were soaring at match time and both players exchange tentative holds to open proceedings.
Del Potro, however, did not take long to make his presence felt, seizing the first break point opportunity that came his way in the third game. He then goaded Khachanov into an erroneous forehand that sailed wide to edge ahead.
The Russian responded with the creation of break opportunities of his own as del Potro attempted to consolidate his advantage but the Argentine stood tall, slapping each away with the gifted flick of his wrist.
Khachanov remained behind and was required to save set points on his own deal in the ninth game. He danced with the Argentine in a grueling backhand exchange before coaxing the error. In the following game, del Potro closed out the set on his own terms.
Set two proved an attritional fifty minutes of tennis, with Khachanov raising his level but unable to break down the resolve of the former Grand Slam champion.
A grueling battle
Del Potro built a head of steam five games in and fashioned double break point on the 21-year-old’s serve, but Khachanov saved both of them. A tiebreak was required to split the pair.
Minibreaks were traded before an exquisite return from the Argentine saw Khachanov dump a forehand into the net for a 5-3 advantage. With two serves to seal the second set, del Potro took full advantage.
The heat was excruciating and the temptation to conclude this affair in double quick time may have played on del Potro’s mind. He was broken for the very first time in the third set, to love no less, to move Khachanov within two games of forcing a fourth set. But he displayed tremendous fighting spirit to recover the deficit as the Russian served to consolidate his advantage.
Again, a tiebreak would be forced to settle the set and it was a breaker to forget for the Argentine. Breaking on the very first point, Khachanov took the tiebreak to love after three hours on court.
The fourth set followed a similar pattern to the previous two, with both players strong behind their first serve. Del Potro, however, sensed an opportunity in the fifth game having raced out to a love-30 buffer.
Khachanov was tiring and he could only stick out his racket and watch the ball sail wide when the Argentine took control of the rally and sent a rasping forehand down the line on break point.
Del Potro was in control and when the Russian netted a forehand on match point, his place in the third round in Melbourne was confirmed.