France captain Guilhem Guirado thought his side had thrown away victory in their Rugby World Cup opener against Argentina when Emiliano Boffelli lined up a last-minute penalty in Tokyo.

Les Bleus claimed a 23-21 victory on Saturday, which could well prove crucial with England also in Group C, but only after Boffelli's last-gasp attempt at three points drifted narrowly wide from 53 metres.

That miss ensured a Camille Lopez drop-goal with 11 minutes remaining was decisive for a France side that had led 20-3 at the interval, only to be comprehensively outplayed in the second half.

Asked what was going through his head when Boffelli prepared to kick what could have been a match-winning penalty for Argentina, Guirado said: "I was thinking the game is finished and we lost the game."

Reflecting on his side's hit-and-miss display, the veteran hooker added: "We never controlled the game and we never controlled the ball in the second half, but we are very proud of the first half because we were very clinical. When we play like this we are very dangerous.

"I don't know [what went wrong after the interval], but we never controlled the ball. We were doing just two or three phases, we were playing a lot of kick-chase. I think we are better when we play with the hands."

Argentina captain Pablo Matera was deeply unimpressed with his side's performance in the first 40, which ultimately left them with just too much to do.

"[It was a] really bad start from us as a team and it's not good enough," said Matera.

"I think France at the beginning didn't do too much, but they took their opportunities and scored points."