JESON Patrombon over the weekend pulled off another big upset over world No. 30 and third seed Dominic Thiem of Austria to barge into the quarter-finals of the Grade One International Tennis Federation juniors in Nonthaburi, Thailand.

Patrombon displayed maturity with aggressive baseline plays for a come from behind 6-4, 6-3 defeat of the clay court specialist Thiem.

The Pinoy netter, under coach Manny Tecson, was trailing in early goings of both sets 3-4 and 2-3 but managed to hang on from long rallies and eventually won.

The 16-year old Patrombon faces Australian qualifier Andrew Whittington, who was also a big 7-5, 6-0 winner over fifth seed Ben Mclachlan of New Zealand.

In the doubles competition, Patrombon failed to sustain his momentum when he and partner Kadchapanan bowed to sixth-seed Mitchell Krugger and Daniel Webb of the US, 4-6, 2-6 in the round of 16.

Meanwhile, fourth seed Francis Casey Alcantara, likewise reached the quarterfinals, with a struggling 4-6, 6-4, 6-4 victory over Austrian qualifier James Duckworth.

The former Australian Open junior doubles champion confronts ninth-seed Suk-Yeong Jeong, a 6-1, 6-4 victor over Kalle Averfalk of Sweden.

In a related development, a tennis academy of the Philippines foundation scholar, Marinel Rudas, continues with her sterling performance, this time in the Grade Four ITF Juniors in Brunei.

Rudas earned her first ITF points in singles by schocking 14th seed Natnicha Ruang Sunrej of Thailand, 6-1, 6-0 to enter the round of 16.

The Pinay setter meets a gigantic task against second seed Amreetha Muttiah of Sri Lanka for a place in the quarterfinals.

Rudas is fresh from her first-ever ITF doubles finals last week in Malacca, Malaysia whre she and partner Naito of Japan lost to their Russian rivals.