Grandmaster Rogelio Barcenilla pulled the rug from under GM Tamir Nabaty as the Philippines battled favored Israel to a 2-all deadlock in the sixth round of the 44th Chess Olympiad in Chennai, India Wednesday.
The 50-year-old Filipino, playing black on the second board, pounced on a dubious exchange sacrifice by Nabaty in the 39th move to produce the big upset.
In a game that started as King's Indian defense, Nabaty gave up his rook for a knight to create two connected passed pawns on the queenside.
But Barcenilla quickly extinguished the threat by simply activating his rooks.
Nabaty lost the twin passed pawns and eventually a major piece. He resigned after 64 moves.
The win made up for the defeat suffered by IM Paulo Bersamina at the hands of GM Evgeny Postny on the last board.
A series of weak moves led to the loss of the queen on the 30th move and the Filipino promptly raised the white flag after 41 moves.
The rest of the matches ended in draws.
GM Mark Paragua, playing white, halved the point with GM Avital Boruchovsky in 59 moves of a Four Knights Game.
Paragua agreed to a draw despite a rook up as Boruchovsky had a pawn just two squares of being promoted.
GM Darwin Laylo chalked up his second straight draw this time with GM Illia Smirin after 33 moves of a Queen's Pawn Opening.
The Filipinos slipped into a tie for 14th spot with 9 points, 3 points behind solo leader Armenia which posted its sixth straight win at the expense of India 2, 2.5-1.5.
A win is worth 2 points while 1 point is awarded for a draw.
Top seed United States edged Iran, 2.5-1.5, to take solo second with 10 points.
The tournament takes a break on Thursday before the Filipinos resume their campaign against fifth-seed Poland in the seventh round on Friday.
In women's play, the Filipinas were held to a 2-all tie by lower-ranked Ecuador.
Top board player WGM Janelle Mae Frayna took a much-needed break as WIM Kylen Joy Mordido saved the day on the last board following her 35-move win over Analia Karen Miranda Vargas of an English Opening.
WIM Jan Jodilyn Fronda, playing the first board, split the point with WGM Carla Heredia Serrano after 76 moves of a Caro-Kann.
Also halving their match were Filipina WIM Marie Antoinette San Diego and Josselyne Penafiel Mendoza after 52 moves.
The Filipinas were in a tie for 48th place with 7 points. They take on Bolivia on Friday.