Toney, Brentford's top scorer in each of the last three seasons, is serving an eight-month ban for breaching betting rules and cannot return to action until January 16th.
However, manager Thomas Frank has guided Brentford to ninth in the standings and they travel to Anfield on Sunday on the back of a three-match winning run.
"Super-challenging to play Thomas Frank and Brentford, for different reasons. They do really well.
"I'm not sure they are 100% happy with the season, but losing Ivan Toney – the player he was for them – really is brutal," Klopp told reporters.
"But they are stable in the table, that's probably what Brentford want - getting through this situation and then when he is coming back, using him again.
"It's well organised, they had a few problems in the season, I would say, to get used to the game without Ivan. But when you look at the table they are in the middle with a tendency (of)going up."
Liverpool's Alexis Mac Allister will miss the game as he serves a one-match suspension but Klopp said there was a possibility of Trent Alexander-Arnold playing in midfield.
Alexander-Arnold played there in the League Cup win over Bournemouth this month when the full back provided the game-winning assist.
"Yeah, (it is) a possibility, it depends on the situation, the opponent, on a lot of things. We know that he can play there," Klopp said.
"For us, if we just put him there then we lose one of the best right backs in the world, so we should not forget that completely. Of course, he is an option for that position."
Wataru Endo is also an option and Klopp said the Japanese player would start more league games when he finds his rhythm.
"Wataru makes steps every day and that's important. We had stories like this in the past... Andy Robertson didn't play for half a year, nobody can remember it anymore but it was like that," Klopp said.
"Other players as well had their struggles in the beginning, that's all fine. He didn't even struggle, we played pretty good and he is super important for us."
