Haaland has been the Premier League's top scorer for the last two seasons and the Norwegian has already netted seven goals in three matches this season, including two hat-tricks.
"Close to impossible," Frank told reporters on Thursday when asked how he would contain the threat of Haaland, who has 70 goals in 69 Premier League appearances.
"A lot of teams have tried to neutralise him. I think he's a great player. I think his movements in the box is probably some of the best we've ever seen.
"The way he anticipates and is constantly on the move and focused and aware of where to position himself. That’s top level... he's a decent player in the best team in the world."
Haaland scored the winner in the corresponding fixture last season and had an assist for one of Phil Foden's three goals at Brentford's Gtech Community Stadium.
Frank said Brentford, who have six points from their first three games, could get still something from the league leaders this weekend.
"We know if we hit a good level, we can make it difficult for them," he added.
