Rafael Nadal has pulled out of the Thailand Open due to an injury sustained at the U.S. Open earlier this month, tournament officials said on Monday.

Nadal was advised by his doctor to withdraw from the September 26-October 4 tournament to recover from a stomach muscle problem that bothered him in the U.S. Open earlier this month, Suwat Liptapanlop, president of the Lawn Tennis Association of Thailand, told a news conference.

Nadal lost his U.S. Open semifinal in straight sets to Argentina’s Juan Martin del Potro, who went on to capture his first Grand Slam title with an upset victory over top-ranked Roger Federer in the final.

Nadal cancelled a pre-tournament vacation scheduled to start on Wednesday on the Thai island of Krabi, Suwat said. The injury also forced No. 2-ranked Nadal to sit out Spain’s Davis Cup semifinal win over Israel on the weekend.

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