Villas-Boas is reported to be at grave risk of losing his job if the club are knocked out of the competition by Napoli, after falling well out of Premier League contention already this season and struggling to a 1-1 draw at home to Championship side Birmingham in the fifth round of the FA Cup at the weekend.
Former England captain Terry is still recovering from a knee injury that has forced him to miss the last four games for his club, but he has flown with the rest of the squad to Naples.
"He's a player of great importance," Villas-Boas said. "I will leave it as late as possible and make a decision on him after the training of the team in Naples.
"The team is more important than any individual, but what we are trying to do with John is to respect his importance for the team. We will try to give him a late fitness test to give him every chance.
"There are enough characters to lead on the emotional sense. Of course JT is a great leader, gives you an extra emotional push, but at the moment, we've had to do without him.
"I think there is still enough emotion without him. If he misses out on Tuesday then we will miss a top, top player and a player who gives us great defensive stability. It would be a massive loss for us, that's for sure."
Foremost among Villas-Boas' thinking is the attacking threat presented by Napoli's lively front three - particularly striker Edinson Cavani, who the Portuguese has had watched by his chief scout on more than one occasion.
Reports have linked the former Porto manager with a £40 million summer bid for the Uruguayan striker - should he keep his job - and he admitted he is a huge admirer of the forward.
"He is an amazing player," he said. "To be fair, their strength is in the collective spirit. They have an inner belief in each other. They have a strong front three with [Marek] Hamsik, Cavani and [Ezequiel] Lavezzi. They are a danger.
"It's a different competition. Napoli come into the game after a good result - not after a good run because they've been inconsistent recently - but won well at Fiorentina.
"It's a different type of preparation, different type of football, European football, played in a different way. We will have to be much more competent, play well and try to take the game to Stamford Bridge."