In what would come as a massive blow to India's chances at the Davis Cup, tennis ace Leander Paes pulled out of the US Open mixed doubles semi-finals due to back spasms which also makes him doubtful for the World Group playoff tie against Japan next week.

India's Davis Cup tie against Japan is scheduled from September 16-18 in Tokyo.

Paes and his Russian partner Elena Vesnina, seeded seventh, gave a walkover to unseeded Americans Melanie Oudin and Jack Sock in the mixed doubles semi-finals due to the Indian's back problem.

"Rough day for Leander, back spasms during the doubles. Out of mixed and now in doubt for Davis cup too..hmmmm," tweeted his men's doubles partner Mahesh Bhupathi.

Paes and Bhupathi were knocked out of the men's doubles quarter-final after losing to Poland's Mariusz Fyrstenberg and Marcin Matkowski in straight sets on Thursday.

Photographs: Jay Mandal