Liverpool's preparations for Wednesday's Champions League qualifier against Maccabi Haifa were hit as they crashed to a heavy defeat at FSV Mainz.
Benitez knows Liverpool must improve quickly
Reds boss Rafa Benitez began the friendly with a strong side and the game was goalless at half-time.
But after several substitutions by Benitez, the Germans took command.
The Bundesliga side rattled in five goals from Markus Feulner, Tobias Damm, Ranislav Jovanovic, Chadli Amri and Fatmir Pupalovic without reply.
Benitez knows his side will have to improve quickly, telling his club's website: "We know we need to correct things.
It's not normal to see Liverpool conceding so many goals and that's why I'm not too worried
"We made a lot of mistakes. We need to analyse why things have been going wrong and work hard to fix them.
"We can start next week with a new mentality and I am sure we will be much better on Wednesday."
He added: "The only positive to take from the game in Mainz is that it was a pre-season match.
"It is clear we made a lot of mistakes and gifted them a lot of goals but it was not an official match.
"In the first half I thought we were the stronger side but after the break we made too many mistakes.
"In fact we have made mistakes in all three of our European friendlies and that's not normal for us.
"It's not normal to see Liverpool conceding so many goals and that's why I'm not too worried."