Rafael Nadal's wrist troubles appeared to resurface as he suffered a 6-1 6-3 thumping at the hands of Borna Coric in the third round of the Western and Southern Open.
The world number five eased past Pablo Cuevas in the second round, but was comfortably beaten by 19-year-old Coric on Thursday.
After a hapless showing in the first set Nadal received treatment on his troublesome arm, but, despite displaying some fight to break Coric's serve for the first time in the second, he bowed out.
A wrist injury forced Nadal to pull out of Wimbledon in June, but he returned after over two months out to compete at the Olympic Games in Rio.
The Spaniard was beaten in the semi-finals by Juan Martin del Potro before losing the bronze medal match against Kei Nishikori, though he won gold in the men's doubles alongside Marc Lopez.
Nadal played 11 matches in the space of eight days at Rio 2016, admitting at the end of his campaign that his wrist was still not quite right.
It proved evident in Cincinnati as Coric broke Nadal three times in the opening set, the Spaniard winning just three points on his opponent's serve.
Evidently struggling, Nadal called for his trainer ahead of the second set and received treatment on his left ankle and left arm.
It was not enough to inspire a comeback, with Coric continuing to dominate as he converted the first two break points that came his way to take a 4-0 lead.
Nadal managed to win the next two games, but it did nothing to stop Coric's march into the quarter-finals.