The 18-year-old Thapa, who was considered a medal hopeful, was outpunched 9-14 in the much-anticipated bout as India began their boxing campaign on a losing note at the Excel arena here.
The young boxer from Assam started his 56kg bout defensively as he allowed his Mexican rival to dictate terms on him. The Indian trailed 2-4 after the three-minute first round but came back strongly in the second to narrow the gap to 6-7. It looked like Thapa would turn the tables on his rival with a flurry of left-right punches in the second round from which he took four points to the three of his rival.
He was looking good at counter punches and it seemed that Thapa would wear down his Mexican rival to seal the issue in the third and final round. But it was not to be as Thapa was beaten black and blue in the final round and he had to run for covers.
The Indian had no answer to the flurry of punches -- left and right -- from the Mexican who seemed to have saved his best for the last. In the last 30 seconds, Thapa, already trailing, had to save himself from the marauding Mexican who grabbed seven points as against three of the Indian in the final round.