Chelsea captain Cesar Azpilicueta believes Wednesday's meeting with Valencia is a "must-win" game, with N'Golo Kante also recognising the importance of the encounter as the Blues look to reach the Champions League knockout stages.
Frank Lampard's side are locked in a three-way battle to qualify from Group H, with the Stamford Bridge outfit tied on seven points with both Valencia and Ajax.
Victory at Mestalla would put Chelsea on the cusp of the last 16 and help put to bed the hurt felt on matchday one when the Spanish side left west London with a 1-0 win.
And Kante, who opened the scoring as Lampard's team slipped to a 2-1 defeat against Manchester City on Saturday, insists another defeat could be critical for his side's chances of European success.
"It is another important game. Maybe this is it for the qualification in the Champions League. We need to rest a bit and focus on Wednesday," Kante told reporters.
"Of course, of course, [we mustn't lose]. Three points are needed for the Champions League game and we need to be ready for this game.
"They won [at Stamford Bridge], it was like this, but now we all have seven points and it is really important for us to win and we are going to work for it."
Azpilicueta echoed the thoughts of the talismanic central midfielder as he prepares to return to his homeland for the crucial midweek fixture.
"It is a must-win. We have a great chance to really close the qualification for the next stage," he said.
"We have to take the game like a final because we can qualify there. We play against a good side that beat us at the Bridge in the first game.
"So we have to recover well from the game. Our heads have to be ready for that game because it is a final.
"When you are at Chelsea every game is important. Every game you have to go to win and that's the mindset for the next game."