Villas-Boas has not considered Modric to be part of his plans this season, due to his proposed £40 million transfer away from White Hart Lane, and as a result the Croatian player has been training on his own.
The 26-year-old did not travel with Tottenham on their tour of the United States recently and was not selected to play in Spurs' 1-0 win over Watford in a friendly on Sunday.
But things could change rapidly if Modric decides to remain in London, with Villas-Boas saying the club would do everything possible to get his fitness back up to speed.
"We have to move on, preparing the squad, thinking that the offer might arrive. If not, then we need to get him physically ready as quickly as possible," Villas-Boas was quoted as saying in The Times.
"We respect the mental state of the player and don't want to affect the running of the squad [by him joining in]. That is the most important thing.
"The individual is a good professional and is going through a difficult situation, but the club can do nothing about it.
"It is the second time he has had this situation. When he is mentally ready we will build him up physically. It is very difficult to do that to play the first game."
Local newspaper reports in London mention a disagreement between Tottenham and Real Madrid over the valuation of Modric.
Spurs are reported to be seeking £40m for the creative midfielder while Madrid are thought to have offered close to £28m for his services.
