An indication of how poor Liverpool have been this season is that Portsmouth have lost 14 of their 15 matches against top-half opposition, with the other match a shock 2-0 victory over the Reds at Fratton Park in December.
Benitez's men had revived their hopes of a Champions League place with a solid start to 2010, but another week like the last one will heap even more pressure on the Spanish manager.
Argentina captain Mascherano feels the Reds can use the Portsmouth match as an opportunity to rebuild some confidence and he insists his team's destiny is still in their own hands.
He said: "We have had a look at ourselves. The match in Lille was totally different to Wigan. We know we didn't play well there or create chances.
"But at least against Lille we created a few chances and should really have scored.
"We have got to score against Portsmouth then we will play the game against Lille as a final. Our target is the same, to finish in the top four and to do well in the Europa League. We know if we play well then we can progress.
"Wigan was a very bad game and a very bad night. We didn't work in that game as hard as we can and we could not complain that we lost. Lille was completely different but still we need to improve.
"We've got to think we can win these two games, to get through to the quarter-finals and also get three points to help us in the Premier League.
"It is going to be a very busy week, with Portsmouth, Lille and Manchester United.
"It's very important and we have to keep our focus. Everything is still in our hands."
Benitez is hoping that Yossi Benayoun can recover from an ankle problem that kept him out of the defeat in Lille and Argentinian winger Maxi Rodriguez is also back in contention after being ineligible for Europa League duty.
If Liverpool thought they had problems, the visit of Avram Grant's Pompey should remind them that everything is relative.
The Fratton Park club are still waiting to discover whether they will be hit by a nine-point deduction after going into administration but they are well adrift at the bottom of the table with just one win in their last 10 Premier League matches.
But the Reds' current plight has left Portsmouth?s Marc Wilson confident that Grant's men can pull off another shock at Anfield.
Wilson said: "I don't think the lads mind where they go at the minute and I think Liverpool are having a bit of a hard time.
"I watched them play against Wigan and I don't think they are playing the best football - but on their day they are as good as anyone.
"Maybe they are thinking "It's Portsmouth, they are bottom of the league so it's going to be an easy win". Maybe we can get on them.
"They are definitely beatable, I have seen Portsmouth beat them in the past as well."
Source: AFP European Edition