Alisson says he was overawed by Liverpool's supporters while playing for Roma last season.
The Brazilian arrived at Anfield in the summer, but has revealed he was already sold on the atmosphere on Merseyside during last season's Champions League semi-final.
Speaking with the club website, the Brazilian goalkeeper said: "It's difficult to play against Liverpool. The quality of the team is amazing. And then the 12th player, outside the pitch, that is the supporters.
"Last year, I can remember about the semi-finals that they played against us, it was difficult. It was an unbelievable atmosphere. It was incredible.
"I like to play with supporters of the other team shouting, talking to me. But here was something different.
"When I signed, when I wanted to come here and I knew about the interest of Liverpool, yes, for sure [that experience was a factor].
"We players, we want a team that wants you, a team with quality with a good manager and with great supporters. I think here at Liverpool you have maybe the biggest supporters in the world."