Spurs suffered a crushing blow as they lost 3-0 to the visiting Hammers, ending their unbeaten home record this season.
The Portuguese recognised that the visiting side played extremely well, starting things off with an effort that allowed Winston Reid to open their account in the 66th-minute.
Six minutes later, West Ham surged forward again with Noble tearing into Tottenham's defense, parrying the ball to Vaz Te, who finished with a slightly fortuitous goal.
“That was probably the key to the game,” reflected Villas-Boas.
“We looked to go to two strikers to have a go, but that’s when 2-0 happened and made it very difficult for us to come back into the game.”
“We were unlucky not to score at the start of the second half and then ended up chasing the game from a difficult position.”
With three goals in just 13 minutes in the second half, the effort from the Hammers had given them their very first loss by more than a single-goal margin in 32 matches and their second home loss in the last 16 Premier League matches.
Playing without a striker, Sam Allardyce set out to confuse and frustrate Tottenham from the very start, a strategy that saw them score their very first away goal of the season in dramatic fashion, and adding two more in quick succession.
“You can always be vulnerable against teams that defend well, control the spaces well and make it difficult," Villas-Boas continued.
"They look to hit you on the counter and West Ham did that well. They deserve credit for what they did.”