Vieira – a three-time winner of the competition as a player – guided Palace to the semi-finals last year in his first season in charge.
A competitive mentality will be key to coming out on top on Saturday, Vieira believes, despite Southampton sitting bottom of the current Premier League table.
“I think that is just the quality of the Premier League,” Vieira reasoned. “You look at how tight the league [table] is.
“That league table doesn’t reflect the quality of the games that they [Southampton] have been playing. For us, it is about having the right mindset to compete well and, of course, try to go into the next round.
“There is no doubt that everybody wants to do well. Everybody’s working hard to do well. We have to believe in the process.
“You’re going to go through difficult periods and that is why I always say it is important to try to manage the emotional side of the game.
“It feels like a Premier League game. It is the FA Cup but it’s going to be as difficult as a Premier League game. That is what we expect. We are not going to be surprised by the quality of Southampton.
“The biggest mistake we could make is to look at the table. I don’t think they [Southampton] will be there at the end of the competition. If we are not mentally prepared, it will be difficult.”
Vieira has also enjoyed witnessing the promotion of Academy midfielder David Ozoh to his first-team outfit this season.
The 17-year-old was named in a Premier League matchday squad for the very first time in Palace’s recent win at Bournemouth.
“He has really grown since he’s been with us,” Vieira noted. “He’s been training with us [the first-team] really often, and adjusting himself to the tempo of the game, but he’s got the strength, the power and the technical quality to train with us every day.
“There is still a long way [to go for him]. He is just 17, and he was playing last year in the Under-18s, so he was playing up in the Under-21s. Now, he’s training with the first-team.
“He found it really difficult in the first couple of weeks but now he’s starting to get used to it. We have to give him time to grow and get used to being around the first-team players before asking him [for] too much.
“You have some young players who have a lot of attributes, but when they are around first-team players, they don’t have the courage or personality to play with this kind of freedom, so you’re looking at all those kinds of aspects.
“David’s been really good so far.”