Frank Lampard admits Chelsea can't afford to lose against Valencia on Wednesday night.
Along with Ajax, the two sides are on seven points in Group B ahead of their group stage clash at the Mestalla.
And Lampard says the Blues must walk away with at least a draw.
"It's a must-not-lose game," said Lampard, who knows his team will advance with a win and still have qualification in their hands if it's a draw.
"We lost ground in the first game against Valencia, we have made up a lot of that ground, but I always thought it would be a tight group. It's meant we have had to go to two difficult stadiums against two difficult teams and win.
"It doesn't mean we're out if we lose, but it puts us in a very difficult position. What we have done is bring that kind of knockout football slightly earlier in the competition. That's no big problem. The reality is at this level you will come to this conundrum at some point where it will be like this.
"Work remains to be done and another challenge is in front of us."
