Cramping Australian James Duckworth has bowed out of the Australian Open in the second round to Slovenian Blaz Kavcic in another marathon match.

Playing in searing heat at Melbourne Park, the 20-year-old Sydneysider courageously saved five match points in the final set before going down to the world No.93 3-6 6-3 6-4 6-7 (3-7) 10-8.

Duckworth had already battled through a four-and-a-half-hour, five-set encounter to topple his great mate and compatriot Ben Mitchell in the opening round.

But Thursday’s clash with Kavcic was an even more gruelling affair.

At four hours and 52 minutes, it was the longest match of the tournament on the hottest day so far.

The Slovenian twice called for the trainer early in the deciding set but, by the end of the match, it was Duckworth who was cramping badly in both legs.

With the temperature nudging 40 degrees, Duckworth took the match into a do-or-die decider with an impressive display in the fourth-set tiebreaker.

The Australian twice went down a break in the fifth and was able to claw it back, only for Kavcic to finally clinch the match and advance to the third round of a major for the first time in 11 attempts.

The Slovenian had eliminated Lleyton Hewitt in the first round of the French Open last year.

He will meet Frenchman Jo-Wilfried Tsonga in the third round.