The England international did not even make the substitutes' bench for the 1-0 win over Reading but Lambert stressed he is still part of his plans.
"He just has to play well and train well, that's a simple one. I am not going to break something or reinvent the wheel," Lambert told Sky Sports when asked what Bent had to do to try and regain his place in the team.
"That is something that football people understand. He just has to pay well and at the end of the day, it's always my decision. I need everyone at the football club to perform and try and do well."
Christian Benteke, who has been preferred up front to Bent, scored the only goal of the game and Lambert was full of praise for the Belgium international.
"He is an absolute credit to the game of football," added Lambert. "For someone who is only 22 years of age, he has been absolutely fantastic."
There was also praise for the team as a whole, with the win over Reading coming just three days after they held Arsenal to a 0-0 draw.
"I know the effort has been absolutely fantastic," said the Scotsman. "To play Arsenal and go again on the Tuesday was a big, big effort and I am delighted with them.
"Even when you are up against the bigger teams, the onus is on the home team to try and come out of the blocks. I have got to give them a lot of credit for carrying on going."
A crowd of just 28,692 turned up at Villa Park but Lambert is convinced the fans have a role to play if they are to advance up the Premier League table.
"The crowd are absolutely vital," he said. "They have been magic since I have been at the club.
"If the crowd sticks with us, hopefully we can give them something back."