A 1-1 draw at Belgian side Racing Genk and 2-1 defeat at Bayer Leverkusen have undermined Chelsea's challenge, but they will reach the last 16 for a ninth successive season by beating Valencia in their final Group E match or a eking out a goalless draw.
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The sides have met five times in the competition with Chelsea winning twice and three matches drawn but Valencia are currently in better form.
Chelsea have lost five of their last 10 matches in all competitions and although they played well in a 3-0 win at Newcastle United on Saturday, shambolic high-line defending and a lack of creativity in midfield have placed a heavy burden of responsibility on the London side's strikers.
Villas-Boas can no longer rely on the ageing John Terry or erratic David Luiz at the back and the young Portuguese manager will hope that the impressive young England international Daniel Sturridge continues his sharp form.
He scored his seventh league goal of the season at Newcastle where the experienced Didier Drogba was also on target.
While Chelsea were winning at Newcastle, Valencia scraped a 2-1 home win over Espanyol in La Liga to maintain their grip on third place but coach Unai Emery had to abandon plans to rest Roberto Soldado, bringing his captain off the bench to score the 80th-minute winner.
The in-form striker, who is making a strong case for inclusion in Spain's squad for next year's European Championship, took his La Liga tally to nine goals and has five in this season's Champions League, including an equaliser from the penalty spot against Chelsea and a hat-trick in the 7-0 drubbing of Genk.
Soldado said having to battle past Espanyol would stand the players in good stead for the game at Stamford Bridge.
"It was a really tough match and we suffered a lot but we showed we knew how to cope with it which will be important for Tuesday when we are bound to suffer again," he told reporters.
"If we had lost today [Saturday] it would have put a different complexion on Tuesday's game, which will be like a final," added the 26-year-old former Real Madrid player.
"A win today confirmed the team's positive dynamic and we are winning games and getting good results and that is important for our confidence before we play Chelsea, who we know are one of the world's best teams.
"We know it will be an extremely difficult match but without doubt we will be at the required level and we hope to return home with the result we expect."
Probable teams:
Chelsea: 1-Petr Cech; 2-Branislav Ivanovic, 26-John Terry, 4-David Luiz, 3-Ashley Cole; 7-Ramires, 8-Frank Lampard, 6-Oriel Romeu, 10-Juan Mata; 23-Daniel Sturridge, 11-Didier Drogba
Valencia: 1-Diego Alves; 23-Miguel, 4-Adil Rami, 18-Victor Ruiz, 22-Jeremy Mathieu; 19-Pablo Hernandez, 5-Mehmet Topal, 24-Tino Costa, 17-Jordi Alba; 7-Jonas, 9-Roberto Soldado
