But, despite seeing Spurs lose 2-1 Neil Warnock's side at Elland Road, the Portuguese insisted he is "happy" with his current options.
He told reporters: “It is something we have discussed at length in press conference. We are happy with the options we have, but we understand injuries can put us in a difficult position.
“Obviously Ade [Adebayor] is at the Africa Cup of Nations and he has already missed a couple of games, but we have to see how he progresses in the competition and then have him back.
“He [Defoe] got a knock in training unfortunately ruling him out of this game. He will definitely be back for the Norwich game.
“I think, as I have told you before we are comfortable. It [not signing anyone] is a risk we are willing to take."
Villas-Boas made five changes from his side's 1-1 draw with Manchester United last time out, but the former Porto boss dismissed suggestions that he is focusing solely on the Premier League.
“No, not at all. We wanted to go through. We had full confidence in the players picked, we did not make any aggressive chances," he added.
“Obviously we wanted to win, and do well in this competition, but we have been knocked out by a Leeds team who played better today and you have to give credit to them. We should have done better defensively and created more opportunities.”
The 35-year-old went on to bemoan the hosts' early goal - scored by Luke Varney - as the primary reason for Tottenham's defeat.
“It was very competitive. Reflecting on the match it was important we didn’t lose an early goal first, that gave them extra stimulus. I think if we had gone one-up in the first few minutes it would have been a different game.”