The Royals come to St Mary's sitting one place and three points behind Southampton in the Barclays Premier League standings.
A Saints victory could see us move away from our opponents in the same manner that last month's 3-1 win at QPR did, and Fonte is under no illusions that this weekend's game is similarly important.
"It's a massive game for both of us, and we're aware of that," the Portuguese said ahead of the game.
"With that pressure, it's going to be an energetic and tough game but we're looking forward to it.
"We've been preparing ourselves very well this week and we have our game plan so we'll try to win on Saturday. There's a lot of pressure, so it's about trying to stay calm and knowing your job.
"As a team, we have to work hard to get the better of them – it's as simple as that.
"As we know, it's a hard division and it's proving to be so for Reading as well," José continued.
"We know they can score goals, especially from set-pieces, but they've been struggling with the goals conceded.
"I predict a very hard game against them because we're fighting for the same thing – we want to get out of the bottom three.
"We know them from last year and hopefully we can get the better of them."
Fonte has played his part in a considerable improvement in Saints' defensive performances, with just four goals conceded in the past five league matches.
Compare that to a record of 28 in the previous ten, and the signs of progress are obvious.
Of the back four that has started Saints' last five games, two – Nathaniel Clyne and Maya Yoshida – were signed in the summer while 17-year-old Luke Shaw did not make his league debut until last month.
"You need time to understand each-other because it's not a straightforward thing," says Fonte, who is the only player to have been on the pitch for every minute of every league game so far this season.
"It was question of learning quickly. We had a lot of new players who came into the team – of the current back four, only I played last year – and that makes it more difficult because you don't understand each-other.
"You need to play with [other players] to understand what they normally do in certain situations.
"The fact that we haven't changed the players around has helped because people start to gel and understand each-other more.
"We stuck together. A couple of the players are 20 or 21 – and even younger in the case of Luke Shaw – so it takes time to get better.
"We've been getting better and better, so hopefully we can keep going like that and improving.
"We are very pleased that we have been stopping goals coming in, so we've been doing well as a team and we want to keep it that way.
"We have to keep defending well because it's very important to keep clean sheets in this division."