Defoe scored 13 goals before Christmas before having his form and fitness hampered by a troublesome pelvic problem.
The 30-year-old failed to hit the target in 12 straight matches, but his sharpness and eye for goal returned on Sunday when he stepped off the bench to score the second goal as Spurs shocked Manchester City 3-1.
Villas-Boas now has to decide whether to restore Defoe to the starting line-up ahead of Emmanuel Adebayor for Saturday's trip to Wigan as Tottenham look to maintain their bid for a Champions League place.
"Yes, it's a big decision (to choose between Defoe and Adebayor), but we are extremely happy," Villas-Boas said. "It's very important for us to have Jermain back, particularly because he found the back of the net.
"Goalkeepers have been making impossible saves against him and he finally got the ball in the net the other day with a tremendous goal that helped us get the three points.
"It's good because he had a blip in terms of goals, not performances - he was always sharp - but he had a couple of injuries. Now he is back he gives us that quality and confidence by scoring."
Villas-Boas also confirmed that England winger Aaron Lennon will return to the squad at the weekend after three weeks out with a knee injury.
"He has been training with the team all week so he will be available for selection," he added. "He is a good player to have back, he has had a tremendous impact. It is another big boost for the squad."