Bale's future at White Hart Lane remains uncertain after Real Madrid launched a world record bid to sign the Wales international.
Last season's Footballer of the Year recently told Villas-Boas that he wants to join Real, but Spurs are determined to keep hold of the 24-year-old.
He will miss the opening game of the season against Crystal Palace on Sunday and Villas-Boas is unsure how the transfer speculation is affecting Bale.
"His mental state nobody knows because the player doesn't speak," Villas-Boas told reporters.
"The only thing that we are able to see, or you are able to see, is the player arriving in and out of the training ground."
However, the 35-year-old then appeared to back-track by saying: "It (Bale's mental state) is fine. It's fine."
Villas-Boas also reiterated the club's stance that Bale is not for sale, with just over a fortnight remaining of the transfer window.
He added: "We have explained to the clubs that have asked for him in various ways that the player is our player."
In addition to missing the game against Palace, Bale's foot injury is also likely to rule him out of Spurs' following two fixtures.
"Well at the moment, he hasn't been involved from the first friendly of the season (on July 15) so pre-season has gone by without him being involved so much," he continued.
"So for Palace, for Tbilisi, for Swansea, he will not be in line to threaten to come back."
Another subject Villas-Boas could not clear up was Tottenham's 'partnership agreement' with Real, which was struck up following Luka Modric's sale to the nine-time European champions.
The deal was supposed to herald a new era of co-operation between the two clubs.
"I am not aware (of what the agreement involves) because it is something that was involved with contracts between Tottenham and Real Madrid," Villas-Boas added.
"I am sure there was some kind of protocol agreement for youth levels, for players, I think the option on first loans. I am not sure. So it was agreed with the Modric deal."