Sixth seed Juan Martin Del Potro advanced to the fourth round of the US Open on Sunday by eliminating 62nd-ranked Daniel Koellerer of Austria 6-1, 3-6, 6-3, 6-3.

The 20-year-old from Argentina will play for a berth in the quarter-finals against Spain's 24th-seeded Juan Carlos Ferrero, the 2003 French Open champion and 2003 US Open runner-up.