Mauricio Pochettino's side, by Villas-Boas' own admission, had edged the contest in the first half, but Bale - who previously played for the Saints - kept Spurs' top-four hopes alive with a thunderous effort from the edge of the box.
|11/8||Tottenham are 11/8 with William Hill to finish in the top four
"It [Bale's goal] was a game-decider, a great moment of individual brilliance to decide the game," Villas-Boas told Sky Sports after the game.
"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."
Villas-Boas recognised that Southampton had enjoyed greater control in the first half, with Rickie Lambert thumping the post from a free kick, but the White Hart Lane outfit responded in the second half to claim three valuable points.
"In the first half, Southampton had the better chances," Villas-Boas added.
"We regrouped at half-time, and in the second half we tried hard to get the result. We played our football.
"The fans were amazing; the noise at the Lane was incredible in the last 45 minutes."