Del Potro's great sportsmanship

WATCH: Del Potro shows ultimate sportsmanship to hurt rival

VETERANS Tomas Berdych and David Ferrer have fallen foul of the tennis gods, departing the French Open prematurely, but Juan Martin del Potro has finally caught a Roland Garros break.

The Argentine advanced 6-3 3-6 1-1 when Nicolas Almagro retired with a left knee injury in a career reversal of fortune.

The US Open champion has struggled for fitness since upstaging Roger Federer in New York in 2009 and he took no pleasure out of Almagro's tearful exit.

Devastated for his opponent, del Potro hugged Almagro before packing the Spaniard's racquet bag.

Del Potro will next play world No.1 Andy Murray, who fought back from a set down to defeat Slovakian Martin Klivan 6-7 (3-7) 6-2 6-2 7-6 (7-3).

Wimbledon runner-up Berdych was rolled 7-5 6-4 6-4 by lanky Russian Karen Khachanov, who now faces John Isner after the US 21st seed progressed 6-3 7-6 (7-3) 7-6 (7-2) with 21 aces against Italian Paolo Lorenzi.

A finalist in 2013, 30th seed Ferrer was downed 7-5 3-6 7-5 4-6 6-4 by Spanish compatriot Feliciano Lopez.

Lopez next plays US Open winner Marin Cilic after the Croat overwhelmed Russian Konstantin Kravchuk 6-3 6-2 6-2.

South Korea's Hyeon Chung earned a tilt at Japanese eighth seed Kei Nishikori with a 6-1 7-5 6-1 victory over Denis Istomin.

Nishikori beat France's Jeremy Chardy 6-3 6-0 7-6 (7-5).