Reports have linked the Blues with a move for the Brazilian, who has impressed during Shakhtar's Champions League campaigns in recent years.
However, Villas-Boas has suggested that he is an unlikely target due to his ineligibility to play in European competition.
"Willian is a very interesting player, but he is cup tied in the Champions League," said Villas-Boas.
"I don't think we should go for players who cannot be involved in all the competitions."
The 23-year-old has been capped twice by Brazil.