American Sam Querrey lost 6-3, 6-4 to Romania's Victor Hanescu in the first round of the Chennai Open on Tuesday.
Hanescu next plays Canadian fourth seed and world No. 31 Milos Raonic.
Eighth-seeded Belgian Olivier Rochus also lost, falling 6-3, 6-4 against qualifier Yuichi Sugita of Japan.
''It was one of the best matches I've played,'' 235th-ranked Sugita said. ''This is one of the highest-ranked players I've beaten.''
Predominantly a baseline player, the 23-year-old Sugita counterpunched hard to keep No. 67 Rochus at bay.
Sugita said coming through the qualifiers helped him adapt to the conditions, while Rochus was playing his first match of the new season.
''It was good for me,'' he said. ''I hope to play this well in the coming rounds, and be prepared for the Australian Open qualifiers.''
Edouard Roger-Vasselin of France brushed aside compatriot Eric Prodon 6-4, 6-3 and will meet defending champion Stanislas Wawrinka of Switzerland in the second round.