Vietnam's top chess player GM Le Quang Liem lost to Cuba's Leinier Dominguez Perez in the fifth game of the Spice Cup held in Texas on Thursday.
The defeat pulled top seeded Liem, ranked 25th in the world, to second place behind the 38th-ranked Perez.
In Friday's game, Liem (elo 2717) had the disadvantage of playing with black pieces, making it difficult for him to launch attacks. He lost the game after 59 moves, giving the top spot to the second seeded Perez (elo 2710).
Perez now leads the tournament with nine points while second-placed Liem has eight. The 100th-ranked German, Georg Meier (elo 2648), and Americans Yury Shulman (elo 2608) and Ray Robson (elo 2583), have six points each.
Somewhat surprisingly, 77th-ranked Sabastien Feller (elo 2668) of France is now at the bottom with only two points.
The players will have a day off before the second leg matches start on Saturday.