New Liverpool owner John Henry was in attendance at Anfield to see his team recover from being a goal behind after 45 minutes and looking bereft of ideas to storm back in the second half to claim a vital win and almost book their place in the next phase of the Europa League.
The introduction of Gerrard in the second half was the catalyst Liverpool needed to inject some urgency into the proceedings and turn the game around.
In the first couple of minutes the Reds found space down the flanks to send over a series of dangerous crosses and expose the uncertain keeping of the Italian stopper Morgan de Sanctis.
But when the breakthrough failed to arrive the visitor’s regrouped and showed their attacking prowess in which Ezequiel Lavezzi was outstanding causing the Liverpool defence problems with his pace and movement.
The first warning for the home side was when Marek Hamsik blazed over from a good position.
The Italian’s continued to press as Liverpool laboured to create anything of note in attack.
The home side were also making mistakes and giving away possession too easily. From one such error Lavezzi pounced but fired narrowly wide.
But the Argentinean got his reward after 28 minutes. Further sloppy play in the middle of the field allowed Edinson Cavani to head Lavezzi clear and his crisp finish gave Pepe Reina no chance.
The vociferous Napoli supporters celebrated accordingly.
The whole team was inspired by the introduction of Gerrard and Napoli looked shocked with the more positive attitude of the hosts.
Gerrard gave the Italians due notice of what was to come when he fired a free kick narrowly wide.
Then on 75 minutes the England midfielder began his quest for the match ball.
A poor back pass from former Reds defender Andrea Dossena was pounced upon by Gerrard who forced the ball home in a challenge with the keeper.
With four minutes remaining Johnson was brought down inside the penalty area by Salvatore Aronica and the Reds skipper did the rest from 12 yards.
The hat-trick arrived shortly after when Liverpool broke quickly through a ragged visitor’s rearguard allowing the super-sub to coolly chip De Sanctis and go home with the match ball.
This result means the Reds have won their last eight European home games and only need to avoid defeat in Bucuresti to progress in the competition.
Referee: Fredy Fautrel (FRA)
02 G Johnson (yellow card)
16 Kyrgiakos (yellow card)
04 Raul Meireles
28 C Poulsen (Eccleston 65)
14 Jovanovic (Gerrard 46)
24 Ngog (Lucas 82)
26 De Sanctis (yellow card)
08 Dossena (yellow card)
14 Campagnaro (yellow card)
17 Hamsik (Yebda 84)
07 Cavani (yellow card)