Andy Roddick has withdrawn from next week's Japan Open due to a hamstring injury sustained during the Davis Cup.
The US Open champion, ranked No 2 in the world, sent organisers a letter saying he hurt his right hamstring during Friday's singles loss to Slovakia.
On Sunday, Roddick assured the United States a place among the top 16 Davis Cup teams next season when he beat Karol Beck in straight sets.
Roddick had already pulled out of the Thailand Open on Monday.
ATP executive Weller Evans said Roddick would be fined $40,000 (€34,000) for his late withdrawal from the tournament, the first ATP event in Thailand.