French forward Maupay returned to his former club ahead of the transfer deadline on a season-long loan from Everton, where he scored just once following his arrival from Brighton in August 2022.
Maupay sat out last weekend’s Premier League game against his parent club, which ended 3-0 to the Toffees.
With striker Ivan Toney continuing his Football Association ban for breaching gambling rules and Germany forward Kevin Schade now set for an extended spell out injured, Maupay could be brought back into the attack for Sunday’s trip to Nottingham Forest.
Maupay scored 37 league goals for the Bees between 2017 and 2019 as the West London club built towards promotion from the Sky Bet Championship.
Frank has been impressed with Maupay’s attitude as he looks to kickstart his career again.
"Neal has settled in more and more to the way we do things. It’s very nice to have another quality player who can affect the game," Frank said.
"He trains like a beast - he pushes himself and the team. He is getting closer and closer with the relations and connections."
Brentford head to the City Ground on a winless run of six games following defeat by Arsenal in the Carabao Cup on Wednesday night.
Frank, though, feels the mood in the camp remains positive.
"After a game if you don’t win, everyone is irritated and frustrated, then the day after you are a bit more positive and in the process of what we did well and what we need to improve," Frank told a press conference.
Forest sit a place above Brentford in 12th heading into the weekend’s games.
After a 1-0 win at Chelsea, Steve Cooper’s side drew with Burnley and then were beaten 2-0 at Manchester City last weekend.
"Nottingham are a good team," said Frank, who will also be without Mikkel Damsgaard following the midfielder’s minor knee surgery.
"They have improved the squad with several very good players, and we know that they are a very difficult team to face at their home ground.
"The game we will play on Sunday will be incredibly even and difficult. It will be the small things that decide it.
"There is no doubt the Premier League is growing in level and quality. You can see the amount of money every club is spending on players.
"The quality of the teams is so good. The difference between the bottom 13 is very, very even."
Frank added: "It will be a difficult task, but we trust ourselves and we know that we can go there and win."