Toulouse, the defending champions, will take on Racing in Toulouse this weekend as they look to reach the semi-finals for the 20th straight time.
But they could be without Picamoles after he suffered both calf and shoulder injuries and is now a doubt for the game.
Racing Metro could have secured a home knockout game of their own had they picked up a bonus point win against Castres, but in the end they had to settle for a 29-28 win, which their France hooker Dimitri Szarzewski believes showed the spirit of the team.
He said: "It was half-time which cost us because we were there in the first half but struggled to take our chances. We could have scored a couple more tries and it would have been completely different.
"We went into the changing rooms and said to ourselves Montpellier are a bonus point up so if we want a home knockout game we will need to score tries and get a bonus point of our own.
"We mixed up speed with over enthusiasm. We forgot the basics, we conceded tries on the counter. What we have to remember is that we showed the mental strength to come back and win, that's what we will hold on to.
"We know we are outsiders but in the knockout stages we want to do everything we can to stay alive."