Two-time Olympic medallist P V Sindhu and Thomas Cup star HS Prannoy secured contrasting wins to enter the quarterfinals of the Malaysia Open Super 750 badminton tournament here on Thursday.

Unseeded Prannoy, who won all his matches during India's historic Thomas Cup triumph this year, registered the biggest upset of the day when he eliminated world No. 4 Chou Tien Chen of Chinese Taipei 21-15 21-7 in contest that lasted more than 30 minutes.

Fresh from his semifinal finish at the Indonesia Open last week, the 29-year-old was a slow starter in both the games. But once he gained his ground, there was no stopping the Indian, who sealed his last-eight passage with 12 points on the trot.

The world No. 21 Indian will next face seventh seed Jonatan Christie of Indonesia, against whom his head-to-head record is 3-5.

Former world champion Sindhu took some time to adjust to the game of Thailand youngster Phittayaporn Chaiwan as the world No.7 Indian lost the opening game before pulling off a 19-21 21-9 21-14 win in a 57-minute duel.

Sindhu, seeded seventh, will next face her nemesis Tai Tzu Ying of Chinese Taipei, against whom she has a lopsided 5-15 head-to-head record including a string of five losses on the trot.

Against Chen, Prannoy started from behind in the first game when his fancied rival raced to a 4-1 lead but the Indian slowly found his feet in the court, pushing the world number 4 to corners with his powerful angled smashes.

Prannoy slowly clawed back to 4-6 before levelling it 6-6 and 7-7 and then up 12-8 finding some good angles to put pressure on his rival.

The Indian then fired a cross-court winner to make it 11-8, before cruising to a six-point lead.

There was no looking back thereafter as Prannoy made it 18-13, with his Chen unable to gauge the Indian's deceptive finishes and misjudged his returns.

Prannoy then produced a cross-court drop shot to pocket the first game in 17 minutes.

The duo once again put up a neck-and-neck fight to start off the second game but Prannoy found himself trailing early on before making it 4-4.

Chen looked to bounce back and had the serve at 7-9 but Prannoy once again made his presence felt and did not allow his opponent to win a single rally.

Prannoy then slammed 12 points on the trot to register his second win against Che from six encounters.

Earlier in the day, facing the Thai 21-year-old for the first time, Sindhu took some time to assess her opponent's deceptive style of play.

Sindhu didn't let the opening game slip away and kept things close before the 21-year-old produced a straight smash to pocket the first game.

Sindhu got her acts together after the change of ends and drew level, winning the second with a breeze.

In the third game, the youngster showed some fight and held the fancied Indian 10-10, before she displayed the best rally of the match to take it 11-10 at interval.

A fine rally closer to the net gave Sindhu a slender 13-10 lead, before she made it 18-14 and then sealed the contest.

Kashyap ousted; Satwik-Chirag pull out

Parupalli Kashyap, however, failed to make the last-eight round, going down to Thailand's Kunlavut Vitidsarn 19-21 10-21.

Kashyap produced a superb fight and led the majority of the opening game before going down in an intense battle, while the second game was a breeze for the Thai world No. 18 who won 10 points in a row to seal the issue in 44 minutes.

Meanwhile, men's doubles duo of Satwiksairaj Rankireddy and Chirag Shetty gave a walkover to the local pair of Goh Sze Fei and Nur Izzuddin.

"Satwik pulled a muscle in his core. He was better today but not enough to play and with Commonwealth Games around, the coaches and physios advised him to not play. Hence, Satwik-Chirah pulled out," said an official.