Paddy Barnes' bid for another Olympic medal in boxing came to a surprise end, while world champion Joahnys Argilagos was victorious.
Barnes claimed bronze medals in the men's light fly (46-49kg) in London and Beijing, but there will be no repeat in Rio de Janeiro.
The Republic of Ireland's flag bearer suffered a narrow loss to Spaniard Samuel Carmona Heredia in the preliminaries on Monday.
Argilagos fared better in the same category, winning a tight bout against Galal Yafai on points.
In the men's heavy (91kg), Evgeny Tishchenko was a victor, while Zhanibek Alimkhanuly beat Brit Antony Fowler in the middle (75kg).
Targeting a third Olympic medal, Barnes fell short against Carmona Heredia, losing a tough battle on points.
Two judges scored the fight 29-28 in the 20-yard-old Spaniard's favour, while the other had Barnes a 29-28 victor.
It was just as tight for Argilagos, winner at the world championships last year, as he edged Brit Yafai 2-1.
Far more convincing was Evgeny Tishchenko, another world champion, who outclassed local hope Juan Nogueira.
"He is a world champion, it was a difficult fight. I thought I won but I try not to be too biased. I'm not going to say that I got robbed. Three-round fights can go anywhere, you can have a bad first round and good second, then it's all on the last round," - a disappointed Yafai said, having come so close to an upset win.
"It did affect my preparations and influence how ready I was for this fight a little bit. I only knew that I would be able to fight on Thursday. It's a pity that politics has influenced our sport as boxers from Russia have never been involved in doping. But I don't feel angry. Our job is to perform so I'm fully focused on this," - Tishchenko said, annoyed by the late decision by the IOC to clear most Russian athletes for the Games.
"I just made the weight this morning. About six weeks ago, I was 58 kilos and now I'm down to 49. Halfway through the first round, I felt so tired," - Barnes lamented weight problems after his shock loss.
Brit Joseph Cordina resumes his campaign against Hurshid Tojibaev in the men's light, while local Robson Conceicao is in action in the same category.