Just before an hour had been played, the Paris Saint-Germain midfielder challenged the Lazio player in the centre of the field but was late to the ball and caught Onazi on the ankle – a blow that ended the 21-year-old's involvement and left Nigeria boss Stephen Keshi fuming.
|WORLD CUP SOCIAL HUB
|Keep up with all the latest news from Brazil and get involved in the debate on Twitter with our new World Cup Social Hub|
"I'm sorry," he told the media after the game. "I've not gone in to hurt him; I'm disappointed because I'm not a dirty player.
"I went into the [Nigeria] dressing room afterwards to apologise."
The PSG star had praise for his side's spirit, having spent much of the opening hour under pressure from their opponents before Paul Pogba's header and Joseph Yobo's own-goal sealed the win.
"We may not have the talent of previous generations but we have the heart and the mind," Matuidi continued. "This is what has put us [in the quarter-finals]."
For midfield partner Pogba, the 27-year-old only had words of admiration.
"He has a great future and he showed that today," the Toulouse-born midfielder enthused of the youngster.