Pompey's victory will ignite hope of survival in the Barclays Premier League.
The result also means Avram Grant maintains his unbeaten record against Benitez after posting two wins and two draws during his time at Chelsea in the 2008 season.
Grant was thrilled to claim the scalp of Liverpool having narrowly missed out to leaders Chelsea in midweek.
"Today we played like a team," he said. "From game to game we are playing better and today we deserved the win.
"We played on Wednesday against a team in first place at home, and we showed ourselves if we can do things well at the bottom of the table we can still surprise the other team, and today it went well."
Pompey midfielder Michael Brown added: "We've been playing well in general. It was a fantastic result for us. "It's a matter of getting some points and three points is fantastic against a strong Liverpool team with a lot of talent. It's an enjoyable day for us."
Grant is hopeful of adding to his squad during the January transfer window, despite reports of financial uncertainty.
"I can only tell what will happen on the pitch, because off the pitch I don't know," he said. "I am positive by nature so I want to believe it will be okay.
"It's more easy to fight on the pitch and we will have a long battle until the end of the season. "I said I am positive we can make the team stronger. This squad is a good squad but we need players to make this squad stronger because also we have the African Cup of Nations.
"I will never understand what they are doing with this in the middle of the season, coming back from heat to the cold. So we need players."
I wish they can
They can I believe.... !!!
They were not only at the foot of the table, they were also a few good points away from the second from bottom side... There is still time to save themselves... But it won't be easy...
i tink they can do it..
just like WBA few seasons back..
Their next few matches won't be easy... Away to WH and Fulham, Home to Arsenal and Birmingham, then away to City and United... lol... tough, tough...
Personally I don't think they can, but even though I'd be surprised if they pull it off, it's still believable at this point. I don't know what Avram Grant has done, but before Pompey players just didn't put in the effort. Now that they seem like they are trying, at least there seems to be a chance.
Personally, i think they can.
under Grant, it is going to be a yes.
West Ham instead may go down.
Even though they are trying very hard to repair the damage done during the first half of the season... It still look very difficult and its not because they are not trying... Its because others are fighting just as hard as well. Like Wolves, Wigan, Bolton and last night West Ham. No one really gave them half a chance but they went out fighting and surprised Chelsea... Portsmouth had a very bad start, so the damage control will be even more difficult compare to the others i belief... Although Grant's arrival will give them a slim chance... But if they are not allow to buy players in Jan... I think its going to be very difficult.