Only captain Steven Gerrard remains from the 18-man squad which featured in Liverpool's last Champions League match, a 2-1 loss at home to Fiorentina in December 2009.,
Manager Brendan Rodgers, who has spent big to bring in the likes of Italy striker Mario Balotelli and England midfielder Adam Lallana, says the side are not nervous about the return.
But as five times European champions Liverpool will have a lot to live up to.
"We have a very young squad and they will gain experience -- it is about embracing it. There is certainly no fear of the competition," Rogers said on the eve of the match against the Bulgarian upstarts. "I think success is about qualifying from the group.
"We will take one game at a time: we are at home in our first game and we aim to perform well and get three points but we will respect them like we would if we were playing Real Madrid."
Source: AFP