Lambert has kept faith in Bennett, who he believes is making progress, but admitted the former Middlesbrough player does need pressure on his place.
"Joe's getting better, there is no doubt," said Lambert. "He has been getting used to the league and the type of player he is going to be up against. Like anybody we will try and improve the squad everywhere.
"You have got to have competition and somebody breathing down your neck for your place but his performances over the last few months have been really high.
"Even in the hard times he didn't hide, I think you can talk about people being brave but trying to take a ball in front of 40,000 people - that's brave.
"To be fair to him, he is a young lad but he has taken a lot on board the past few months."