The prop reacted angrily to criticism of his team's scrum and tight play as they scraped a 19-17 win over Scotland at Murrayfield last weekend.
France, Ireland and England can all still claim the title this weekend but Mas snapped when the assembled media suggested France have been too slow to react to scrum law changes. Asked why they have lost their scrum dominance of the past, the Montpellier player said: "I don't know why, you tell me.
"I have been doing the same things for 10 or 15 years, you want me to change overnight? It [the scrum] is like a child who has lost its bearings, how far will it go? It's a real shame."
Mas defended France's decision to play for the penalty that gave them victory over the Scots, saying: "The main thing is to win, although it was embarrassing not to score [a try] from it."
Meanwhile, Les Kiss, the Ireland assistant coach, warned his side must not be fooled by France's apparently disorganised approach.
He said: "There's a perception that they are dishevelled, that they are in a dishevelled place of chaos, but we have looked at it as forensically and you can see an order to it, you can see what they're trying to achieve."