The Blues captain has missed the last four games with a knee injury and has completed just one full training session since.
But his Portuguese boss is set to take the risk ahead of the tie, having endured speculation over his future of late.
“He’s [Terry] a player of great importance," Villas-Boas told The Mirror.
“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.”
The Blues will take on the feared attacking trio of Marek Hamsik, Ezequiel Lavezzi and Edinson Cavani at the Stadio San Paolo in the first leg of their last-16 tie.
And the former Porto manager explained the importance of the England international centre-back's presence.
He added: "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.”
Terry's England team-mate, Ashley Cole, is thought to have a 50-50 chance of featuring in the tie.
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