Grant feels Pompey quite simply have to pick up three points at Fratton Park tonight against Steve Bruce's side.
It is a clash being afforded similar significance on Wearside, with the Black Cats in freefall and without a win in the Premier League since mid-November.
Grant insisted it's a match his team have to pick up a maximum return from if they are to begin closing the seven-point gap to safety.
Pompey now enter a three-game period in the league where they will take on Sunderland, Stoke and Burnley.
The 54-year-old knows those fixtures are going to have a monumental outcome on his team's fate this season.
Grant said: 'Sunderland is most important.
'We are playing at home and we need the points.
'We need these points if we are going to go forward this season.
'This is a big game. The next three games are against teams around us.
'We are running out of time.
'We will do everything to win this game.
'They are a good team, but I don't see teams who are better than us in the bottom half.
'That is why it's a pain that we are not taking points.
'It will be difficult. Sunderland are a good team, but they are not better than us.
'A team like Derby showed less quality than the others two seasons ago.
'We are not like that, but we need to take points.'
To deliver their first Premier League win in seven outings, Grant knows Pompey are going to have to show a much greater killer instinct than they have of late.
They have hit just two league goals in that period and delivered a worrying habit for wastefulness in front of goal.
Grant said: 'Football is about putting the ball in the net.
'At the moment we are not doing that.
'Everything is going well – the football we play, the spirit and chances we are creating.
'If we continue like that we will take points. It will not last forever.'
Tonight will see the return of a Pompey hero in the shape of Benjani.
Benjani moved to Sunderland on loan from Manchester City during the January transfer window, with many supporters calling for the Blues to make a move for him.
The Zimbabwe international is still revered by fans down on the south coast after his two-year stay, following his arrival from Auxerre in 2005.
Benjani went 14 games without scoring a goal after signing, but won the fans; hearts with his graft and commitment.
He then, of course, sensationally scored at Wigan as Pompey completed the Great Escape.
Grant worked with the striker in his first spell at Fratton Park.
He spoke of his appreciation of the man who joined Sunderland on loan from Manchester City – both on and off the pitch.
Grant said: 'Benjani is a great guy. I worked with him here in 2006.
'He is a great guy and a great player who always gives 100 per cent.
'He gave everything for the team and everything for Portsmouth.
I hope he will not do that for Sunderland.
'He is a good player and a very good person.'
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