The France captain completed a £12m switch from Lyon to Spurs on transfer deadline day, with the 25-year-old viewed as a long-term replacement for veteran Friedel.
However, Villas-Boas maintained the 41-year-old American goalkeeper remains an automatic starter after an eye-catching display in a 1-1 draw against Norwich City.
“When you transfer it’s not written in the contract that you have to play,” Villas-Boas said.
“He has to compete against three good goalkeepers and at the moment Brad is doing extremely well. He deserves to be playing and he’ll continue to do so.”
Meanwhile, Michael Dawson had been linked with a move to Queens Park Rangers last week after the Spurs manager revealed the defender was surplus to requirements at White Hart Lane.
But after a transfer failed to materialise, the Spurs manager has challenged Dawson to break back into the Tottenham first-team after Younes Kaboul was ruled out with a knee injury for three to four months.
“There is extreme competition for that central defence position,” added Villas-Boas.
“Younes’ operation will take him out for three to four months and it is up to Michael to compete.
“I’m sure he will come good. He is an extremely good professional and a club captain. He is looking forward to getting back into the team.”
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