Spurs claimed a 0-0 draw in Rome, but Lloris - who was preferred to Brad Friedel - produced a string of top-class stops.
"It was important for him and he was a great help for the team," Villas-Boas said.
"He was decisive in a couple of moments."
The result means Spurs only have to draw their final game against Panathinaikos next month to make the knockout stages of the competition.
Yet Villas-Boas was disappointed that his team had not qualified in Rome thanks to the linesman's incorrect call over Bale's goal - especially after seeing his team denied three goals in the reverse fixture, which also ended 0-0.
"Against Lazio we've had four goals disallowed. Two of them rightly and two of them not, maybe three," Villas-Boas said.
"It's difficult to see decisions go that way but we move on. We take the result. We are in a comfortable position to qualify."
The draw puts Lazio through, but manager Vladimir Petkovic was also disappointed to not win the game.
"It was a very good performance," he said.
"We played a top team from one of best leagues in the world but we managed to put pressure on them. We deserved three points and I must compliment my players."