Rafael Nadal on Thursday withdrew from next week's Cincinnati Masters due to his continuing knee injury, the Spaniard said on his Twitter feed.
"I can not participate in the tournament in Cincinnati. I'm still not able. I have unforgettable memories of 2008. I continue recovering," the ATP number three tweeted.
The event, last major tuneup before the August 27 start of the US Open, was the third straight summer pullout for Nadal, who also missed the Olympics and this week's Masters 1000 in Toronto.
Nadal last played on Jun 28 at Wimbledon, where he lost in the second round to Czech Lukas Rosol.