Trent Alexander-Arnold also starts on the bench, with Joe Gomez preferred at right-back.
Joel Matip starts ahead of Dejan Lovren in the heart of defence alongside newly-crowned PFA Player of the Year Virgil van Dijk.
With Firmino on the bench, Klopp could opt for a four-man midfield, with Sadio Mane and Mohamed Salah up front, unless Naby Keita or Georginio Wijnaldum are utilised in a more forward-thinking role.
As for Barcelona, Luis Suarez returns to face his former side. Suarez spent three years at Anfield between 2011-14 before making his move to the Nou Camp. He scored 82 goals in 133 games for Liverpool.
Philippe Coutinho will also take on the side he left in 2018.
Sergi Roberto is preferred at right back ahead of the impressive Nelson Semedo, whilst Arturo Vidal is also given a start.