With his third victory in five games, Grandmaster Wesley So on Sunday gave a bit of a boost to his chances of winning the U.S. Chess Championship.

The Minnetonka 21-year-old, moved from third place into second place, but still trails the sole leader, Grandmaster Hikaru Nakamura, by a half point.

So defeated Grandmaster Timur Gareev of Las Vegas on Sunday, winning a pawn on the 25th move and grinding his opponent down in the endgame.

Nakamura also won his game Sunday, and So acknowledged that Nakamura is proving to be the strongest player in the field of 12 grandmasters.

“Upsets can happen, although he’s clearly the favorite right now,” So said in a postgame interview with a commentator at the Chess Club and Scholastic Center of St. Louis.

Players get a point for a win, a half point for a draw and nothing for a loss. With six rounds remaining and trailing by a half point, So has to keep up his winning ways and hope that Nakamura falters, even if that means several draws rather than victories.

Monday is a rest day, and the tournament resumes Tuesday. Next up for So is a game against his former college roommate, Grandmaster Ray Robson. The last time the two played against each other in a high-stakes tournament was last October in the Millionaire Chess Open in Las Vegas. So defeated Robson in the finals to win the $100,000 grand prize, leaving Robson the runner-up with the $50,000 prize.