India's Rushmi Chakravarthi ousted third-seeded Katie O'Brien to book a Commonwealth Games women's quarterfinals place alongside compatriot Sania Mirza.
Top-seeded Mirza also had an easy 6-0, 6-2 victory over Cook Island's Brittany Teei, while Chakravarthi, a 32-year-old with a world ranking of No. 616, made a remarkable comeback to oust O'Brien 1-6, 7-6, 7-5.
Mirza and former top-ranked doubles pair Leander Paes and Mahesh Bhuparti are among the highest-profile players in the draw.
But India is one of the few countries with its top players entered in tennis' debut at the Commonwealth Games. Stars such as former No. 1-ranked Lleyton Hewitt and French Open finalist Sam Stosur of Australia, world No. 4 Andy Murray of Scotland and Marcos Baghdatis of Cyprus are missing.
Murray's older brother Jamie was representing Scotland, but went out in the second round 7-5, 6-1 to fourth-seeded James Ward of England.
In other men's singles matches, top-seeded Somdev Devvarman took only 41 minutes to beat Amresh Jayawickreme of Sri Lanka 6-0, 6-1, showing no sign of the stiffnes he had displayed in beating Devin Mullings of Bahamas in the first round.
Jayawickreme piled up the unforced errors and lost the first set in 20 minutes. The only game he held was to open the second set.
But two other Indian medal hopefuls crashed out of the tournament: Second-seeded Peter Luczak of Australia beat Rohan Bopanna 6-2, 7-6 (5) in one hour and 37 minutes; and fifth-seed Heather Guernsey defeated Poojashree Venkatesh 7-6 (7), 6-3.
Bopanna looked ominous, firing three aces in his first game, but his aggression became a disadvantage. Ultimately, Luczak with better control over his stokes prevailed.
Bopanna saved a break point with an ace and saved two more breakpoints in the sixth game with consecutive aces. But unforced errors cost him the set.
The second set went on serve and was decided until the tiebreaker, which Luczak won despite trailing 4-1. He won five straight points and finished it off with a forehand winner.
