Croatia's Mario Ancic has pulled out of the US Open with a shoulder injury and is unlikely to play in next month's Davis Cup tie against Great Britain.
Ancic would have faced Novak Djokovic in New York
Ancic was due to face third seed Novak Djokovic in the first round in New York but the Serb will now face Robin Haase.
Former world number seven Ancic had only just returned to action after a six-month lay-off with glandular fever.
"There's a big question mark on the Davis Cup," he said. "At the moment if I had to say, it's more no than yes."
He added: "That would be a huge disappointment because two tournaments I really thought I could play, after six months out, was the US Open and Davis Cup. That was really the goal."
The Davis Cup clash with Great Britain begins on 21 September at Wimbledon.
Ancic was expected to give Djokovic an early test in New York.
The Croat, a Wimbledon semi-finalist in 2004, returned to action at the Montreal Masters at the beginning of August and posted an impressive win over Tommy Haas in Cincinnati the following week.
However, he picked up a right shoulder injury, which worsened at the New Haven tournament.