Chelsea boss Andre Villas-Boas has called on the fans to create an intimidating atmosphere at Stamford Bridge against Valencia on Tuesday night.
Chelsea must win to guarantee a place in the knockout rounds of the Champions League. A 0-0 draw will only be good enough if Bayer Leverkusen take something from their game against Genk in Belgium.
Villas-Boas knows from his time as part of Jose Mourinho's backroom staff at Chelsea that the fans can make a difference at the Bridge.
He said: "They can have a massive impact. They will have to unite themselves. I have good memories of top European nights at this club, and I know the atmosphere can be raised here, just like we did in the 4-2 against Barcelona.
"If they do that, we would have the right ambience to take on Valencia with that extra input.''
Villas-Boas refused to be critical of Alex and Nicolas Anelka despite the club agreeing to transfer requests from the players last week.
"The players are not being treated like criminals," Villas Boas added. "It was discussed with the board and the players.
"Their professionalism and integrity will never be in doubt, but we want the right mindset. For players on the transfer list, the reality is that, eventually, the mindset is not the same.''
Striker Daniel Sturridge defended Villa-Boas ahead of the crunch game with Valencia: "The manager's approach is great. The attacking style he's trying to implement in the squad, it does work. In the future, you'll see that it works.
"The team will play attractive football. We've just been unlucky with the way we've conceded a few goals. But we're still a strong unit, we'll continue to be a strong unit, and we will be in the future. We'll always work or him and try hard for him.
"We know he'll be the manager for the next three years. We're not worried about any other manager coming in because we know he's going to be here for those three years.
"It's very important we keep our nerve [against Valencia]. The players we have in the squad are used to playing in big games. They've played in World Cups, Champions League finals and semi-finals and other big matches. The players are well prepared for this."
Valencia coach Unai Emery believes his side has what it takes to progress.
"There is a final for us and one of the teams will have to go out," said Emery. "They are a top team but have had problems and doubts and we need to take advantage. This is a real opportunity.
"For Andre, coming to a big club like this and trying to implement his style and his game takes time. With the way he works, the results will be there in the future. It's not going to be good - it's going to be very good.
"I'm sure of that. They might have struggled a bit so far, but when you want to achieve excellence, as Andre and the club wants, it takes a bit more time."