Villas-Boas refuses to reveal Torres decision
Torres missed Chelsea's last two Premier League matches while he serves a three-match ban following his red card against Swansea on September 24.
The Spain striker is available for European ties and featured in the Blues' last Champions League match against Valencia.
It would be easy to keep faith with that trio but Villas-Boas knows leaving Torres on the bench would be a major snub, however erratic his form has been since his British record Â£50 million move from Liverpool in January.
"The decision is made but I wouldn't like to share it with you. What is most important is he is in the 18-man squad," Villas-Boas said.
"He has been out for quite a long time but fortunately he was able to have some action with the Spanish team to keep him in good form. His attitude in training has been good."
Regardless of who starts in Chelsea's forward line, the Blues are unlikely to be seriously troubled by Genk, who have struggled to repeat last season's success in the Belgian league due to injuries and the departures of key players.
Villas-Boas contributed to that decline by signing Genk's promising young goalkeeper Thibaut Courtois during the last transfer window.
He also confirmed his interest in their gifted midfielder Kevin de Bruyne, who hopes to recover from injury in time to feature on Wednesday.
"De Bruyne has always been an interesting player. He can play in several positions, wide left or in central midfield, and is exceptionally gifted technically," Villas-Boas said.
"He reminds me of the older Belgian players like Enzo Scifo. As you know we scouted Kevin, but we have scouted many players. It doesn't mean they will all join us."
Genk's hopes of causing an upset could rest on a surprisingly pourous Chelsea defence which hasn't kept a cleansheet in the Premier League since the opening weekend draw at Stoke.
Blues goalkeeper Petr Cech believes his defence is still sturdy and has just suffered from the team's renewed commitment to attack this season.
"It is always better when you finish with a cleansheet and we have had a little run without one," Cech said.
"But if you finish the game 0-0 you might be happy with the cleansheet but it is only one point, whereas if you win 3-1 it is three points.
"We want to kill the game with more goals and maybe this is the reason we have conceded a few at the end, but we were unlucky with little details. We are improving and I think it is going to stop."
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