Jeson Patrombon, showing steely resolve, pulled off a stunning 2-6, 7-5, 6-4 victory over 16th seed Campbell Johnson of the United States to barge into the Round of 16 of the Grade 1 ITF/LTAT Junior Tennis Championships in Nonthaburi, Thailand.

Patrombon, 17, erased a 3-4 deficit by winning the next three games in the third set to disarm the world No. 94 American in a game played under extremely hot weather condition. He needed three hours to wrap up the match.

“Our strategy paid off and all the training were put into good use. Jeson was aggressive all the way and I kept telling him to rally the ball six times and above,” said Patrombon’s coach and former RP Davis Cup non-playing team captain Manny Tecson in an e-mail interview.

Patrombon, who slipped to No. 212 in the world rankings, will have to play extraordinarily in the next round to advance as he faces third pick Dominic Thiem of Austria, who thumped German qualifier Patrick Elias, 6-4, 6-2.

Patrombon’s feat overshadowed the victory of Francis Casey Alcantara.

Alcantara had to dig deeper into his bag of tricks before pulling off a 6-1, 3-6, 6-4 win over China’s Gao Xin.

With the win, the 18-year-old fourth pick set up a date with Australian qualifier James Duckworth, who downed 14th pick Barrett Franks of New Zealand, 6-1, 7-6 (4).

It would be Alcantara and Duckworth’s second meeting since the Filipino bet forced the Australian to retire, 7-6 (4), 3-6, 6-1 (ret), in the finals of the Phinma ITF Junior Championships at the Rizal Memorial Tennis Court three years ago.

Patrombon then teammed up with Thai Nuttanon Kadchapanan to clobber India’s Mansingh Athare and Uzbekistan’s Sergey Shipilov, 6-3, 6-3, and march into the Last 16.

The triumph earned them a duel with sixth pick tandem Mitchell Krueger and Dane Webb of the United States, who earned an early bye.

Alcantara was not lucky as Patrombon in the doubles as he and partner, Krittin Koaykul of Thailand, bowed to Germans Matthias Wunner and Patrick Elias, 6-4, 3-6, 10-6.