Defeat ended Spurs' 12-match unbeaten league run - their last defeat also coming on Merseyside against Everton in December - and Villas-Boas said it was harsh on them.
"It is difficult for us to take because we did ever so well to come back into the game in the first half and we started brightly in the second half," he said.
"We lost control of the game when things looked to be going our way, which was more down to a couple of mistakes we did rather than to Liverpool's merit - although they worked very hard."
Villas-Boas refused to blame fatigue after Thursday's 3-0 Europa League win over Inter Milan for allowing Liverpool back into the game.
"I think we looked very strong and the overall performance was excellent - it had nothing to do with tiredness," he added.
"Liverpool pressed us hard on that (Walker) backpass and they deserve credit for that as they put us under pressure very quickly.
"Sometimes moments like this happen and you can't be too negative to a player who has done well in a 12-game unbeaten run.
"Hopefully this setback can serve as an example to move forward."
He praised Vertonghen after the centre-back took his tally for the season to five.
"Jan has been doing extremely well and has adapted to the country very quickly," said the Spurs boss. "He is a defender who scores goals and he showed exactly that quality."