Salah had floundered numerous scoring opportunities in the first-half in a game Liverpool needed to win at all costs to defend their Champions League crown.
The Egypt international passed up chance after chance as Jurgen Klopp looked stony-faced on the touchline.
Soon after Naby Keita had given Liverpool the lead in the 56th minutes, Salah latched onto Jordan Henderson’s through ball, went round goalkeeper Cican Stankovic and fired in from a position barely six yards from the byline, one of the narrowest angles to scored a goal from, curling the ball just past the near post.
Salah’s goal and Liverpool’s second of the night, saw him follow club legend Steven Gerrard in reaching the 20-goal mark in the Champions League or European Cup.
Liverpool subsequently qualified top of their group on 13 points, with Napoli finishing second on 11 points.
By Gerald Dandah