The Blues will be expected to take a huge step towards the knockout stages in their two Group E games with the Belgian runners-up, but Villas-Boas has refused to take anything for granted.
"I think it's going to be difficult," he said ahead of Wednesday night's clash at Stamford Bridge, which is followed two weeks later by the return fixture in Genk.
"When everyone expects you to win, that's when you maybe relax yourself too much and we can't relax ourselves too much."
Six points would put Chelsea in complete control of the group, a position they would be in already but for Salomon Kalou's moment of madness which handed Valencia a draw in their last outing.
The Blues still top the pool on four points, one clear of Bayer Leverkusen and two ahead of Valencia, who face a double-header of their own in the next two and a half weeks.
Villas Boas added: "At the moment, the group is very open, and anything can happen. We lost two points in Valencia that we wanted badly.
"We have to focus and concentrate on getting the six points against Genk."
Doing so would leave Chelsea at least five points clear of third place with just two matches to play, all but ensuring them a last-16 spot.
"It puts you in a very, very good position," Villas-Boas said.
"You have to get the first three points, and then eventually fight for the other three."
Villas-Boas looks certain to unleash Fernando Torres on Genk, if only to give the striker some much-needed game time.
Torres is in the middle of a three-match domestic ban following his needless red card against Swansea last month and Europe is currently the only outlet for his talents.
The sending-off was the latest calamity to befall the £50million man since January's move from Liverpool and came just as he was beginning to show signs of getting back to his best.
The arrival of fellow Spain star Juan Mata has been viewed by some as the catalyst for Torres' mini-revival, something played down by Villas-Boas.
However, the Portuguese did confirm the pair enjoyed a close relationship off the field.
"They have got to know each other a bit better now and they share social behaviour," he said.
"It's the same with the French players going around together, and the Spanish and Portuguese. That's normal."
Chelsea fans have also stuck by Torres and the 27-year-old looks like getting plenty more support on Wednesday night, with the Genk game appearing set to be a virtual sell-out.
That did not look like being the case last month, with disenchanted supporters threatening to boycott the match over the recent hike in ticket prices.
Last month's Leverkusen game witnessed the lowest crowd at Stamford Bridge for a Champions League match since the Rosenborg boycott of 2007.
The crowd looked destined to be even lower against Genk but that now appears unlikely, one possible reason being that supporter attention has since shifted to the upcoming vote of Chelsea Pitch Owners that will decide the fate of the freehold of Stamford Bridge.
Villas-Boas is confident of a bumper crowd on Wednesday night, adding: "It should be okay. I've not heard anything recently."