London: Andre Villas-Boas admits Chelsea's crunch Champions League showdown with Valencia on Tuesday represents a do-or-die moment in his troubled reign at Stamford Bridge.
Villas-Boas's side go into their final Group E fixture teetering on the brink of elimination at this early stage of Europe's elite club competition for the first time.
The Blues looked set to cruise into the last 16 as group winners after taking seven points from their first three matches, but a draw with Belgian minnows Genk and a last-minute defeat at Bayer Leverkusen has left them scrambling just to qualify in second place.
Chelsea need a win or a 0-0 draw to go through to the knock-out stages, with a Valencia victory or score-draw sending the Spaniards through at their expense.
Roman Abramovich, Chelsea's demanding billionaire owner, has never hidden his desire for success in the Champions League and even reaching the final in 2008 wasn't enough for Avram Grant to keep his job once Chelsea were beaten by Manchester United.
So, at a time when Chelsea's spluttering form has already raised questions about his reign, Villas-Boas knows he can ill-afford the humiliation of becoming the first of Abramovich's seven managers to bow out in the group stage.
Villas-Boas can take heart from his side's 3-0 victory at Newcastle on Saturday, but Chelsea's erratic home form will give Valencia plenty of encouragement as well.
Stamford Bridge has been a fortress during Chelsea's most successful periods but three defeats from their last four matches in front of their own fans suggests that is no longer the case.
Villas-Boas denied that playing at home has become a problem, although he admitted his side had been performing better on their travels.
"I'm not saying Stamford Bridge is a problem," he said. "There's a problem with results at Stamford Bridge, but there's not a problem with our fans at Stamford Bridge.
"But we have had good performances away from home. In terms of concentration, we have been also doing well away from home and there is more tension in those games as you play them away, (there is) less relaxation.
"Sometimes extra tension can let you be more concentrated and it might help you in your performances."
Even if Chelsea do qualify, they are likely to finish in second place as leaders Leverkusen will be expected to clinch top spot with a win over Genk.
That would leave Chelsea facing a potential last-16 clash against one of Barcelona, Real Madrid, Bayern Munich or Inter Milan.
Valencia know a repeat of their 1-1 draw against Chelsea at the Mestalla earlier in the competition will send them through and they arrive in good form, having thrashed Genk 7-0 in their last group match during an impressive sequence of six wins from seven games in all competitions.
One of their key figures will be Brazilian goalkeeper Diego Alves, who gave a superb display against the Blues in September.
He has established himself as Valencia's number one after boss Unai Emery dropped his experiment of switching between Alves and Vicente Guaita.
Alves, 26, believes that test of his mental strength will stand him in good stead against Chelsea.
"Teams like Chelsea have so much experience in this competition," he said. "We know it will be hard in London but we have confidence."