Rafael Nadal reached into the third round of the US Open on Thursday after Thanasi Kokinakis withdrew.
The Aussie cited a right shoulder injury.
It is an unfortunate conclusion to the US Open for the 23-year-old, who was making progress in his return from pectoral and shoulder ailments.
Next up for Nadal is South Korean Hyeon Chung, who saved a match point in a massive 1-6, 2-6, 7-5, 6-3, 7-6(4) comeback over No. 32 seed Fernando Verdasco of Spain.