The Reds duo have been in scintillating form since Philippe Coutinho’s £142m move to La Liga giants Barcelona in the January transfer window.
Firmino broke the deadlock at St Mary’s on Sunday evening after Salah’s cross found the Brazilian forward in space in the Southampton penalty area.
The South American returned the favour with a world-class assist to tee up the Egypt international to score his 22nd Premier League goal of the campaign.
Firmino has scored 19 times in all competitions this season, including 12 Premier League goals, to enjoy his most prolific season as a Liverpool FC player.
His team-mate Salah has netted 30 goals in the Champions League and the Premier League since his £39m move to Anfield from Serie A giants AS Roma last summer.
Former Liverpool FC captain Souness is confident that Firmino and Salah can help Jurgen Klopp’s side challenge for silverware this term.
“All the teams who win trophies have more than one person that gets into double figures,” Souness told Sky Sports.
“If you’ve got a couple of strikers who can 20 or thereabouts and a few midfield players who can get 10 or thereabouts, it is giving you a chance and Liverpool have that.
“Those two have got an understanding and Firmino has got a football brain.
“We were talking off-air about what separates the good players from the great players and it is the picture they see – that is Firmino.”
Liverpool FC finished in fourth place in the Premier League table last season in Klopp’s first full campaign in charge.
The Reds lost to Manchester City and Sevilla in the League Cup and Europa League finals under the German coach.
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