"Neymar is fine. I'm a boy, he's a boy - a joyful boy", he said.
They won't have it easy against the Swiss however, as Vladimir Petković's side took on their toughest opponent in their opener and came away unscathed.
Lasmar sought to reassure Brazilian media anxious about Neymar's fitness after he limped out of a training session with a sore right ankle following Brazil's opening 1-1 draw with Switzerland last weekend. And for 90 minutes against Costa Rica, it was more of the same.
The Paris Saint-Germain attacker's anger during the match even spilled over towards his teammates, too, it seems. "Pass the ball, '" he said, confirming that he had pulled a muscle celebrating Philippe Coutinho's opening goal.
Brazil had already had to deal with an injury scare involving Neymar, who left one of the team's training sessions limping because of pain in his right ankle. Costa Rica's only World Cup victory against a team from South America was four years ago against Uruguay.
"Today, I was saddened by his behaviour", said Silva.
After a goalless first half Brazil scored twice in injury time, reward for Tite's insistence his players concentrate and press right to the end. But it wasn't going to be that ball that was going to make us win. "At half-time, I was joking: 'Look at the old man here, I'm 57".
A controversial penalty decision late in Friday's Brazil-Costa Rica game could have been one of the stories of the World Cup, but Neymar's late goal in stoppage time to seal a 2-0 win stole the headlines and rendered his dive 20 minutes earlier relatively meaningless.