Bale's swerving effort was his 20th goal of the campaign and his Portuguese boss spoke glowingly of his contribution to the victory after the game.
"[Bale's goal] was a game-decider, a great moment of individual brilliance to decide the game," Villas-Boas told Sky Sports News.
"We kept pushing. Gareth played three different positions - striker, left, right - to try and get the best out of him.
"Southampton dealt with him well, they were well organised. But, last-gasp, there was a bit more space, perhaps because we were pushing for the winner."
Bale was crowned PFA Player of the Year earlier this week.