The 30-year-old is set to start for the north London club when they face Norwich on Wednesday due to Emmanuel Adebayor's continued participation in the Africa Cup of Nations.
But, with the likes of Internacional forward Leandro Damiao and Celtic's Gary Hooper linked with a January arrival, Villas-Boas believes there is room for one more forward on Spurs' books.
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"We've found consistency in 4-4-2 so eventually we have the possibility to have one more [striker]," Villas-Boas told reporters.
"It's just trying to see if it makes sense. The January market is very demanding. Transfer fees can be ridiculously high."
The Portuguese went on to explain that Tottenham are using a 'blood-spinning' technique in order to help Defoe play through injury.
"In muscle injuries, there is always a risk of it showing up again but the medical department feel positive about it and the player is positive and he knows his body well," the former Porto boss added.
"We believe a lot in growth factor treatment and plasma platelet treatments. It is a technique that we have been using since the beginning of the season. It is not common but does happen from club to club.
"Defoe adhered to the treatment very, very well so we can move forward. You take out the blood from any part of the body and spin it around. The plasma comes to the top and you are able to inject it back into the body. It is the part of the blood that heals injuries."