"When I look at the last couple of weeks that he had in training, he deserves to have a chance,” Vieira said at his pre-match press conference. “Tomorrow he will be one of the players that can start the game.
“[Sam Johnstone] has had a couple of setbacks with injuries, but he’s been back in training with the team and he will be part of the squad tomorrow.
“Like always, I will put out a team that I really believe has a chance to win the game. I don’t use the game to please players. Our objective is to go to the next round.”
Palace reached the FA Cup semi-finals last season, but Vieira says his players have to focus on the match ahead of them rather than dreaming of Wembley – despite facing a struggling Southampton side rooted to the foot of the Premier League table.
“What worked well last year was taking it game-by-game,” he explained. “Of course, we wanted to compete, to go as far as we could and we got to the semi-finals. It was a good experience for the team.
“This year, nothing changes. We don’t take anything for granted. We know how difficult it will be. We will have to perform better than in our last home game to go through to the next round.
“The [players] all enjoyed the good run we had last year. The majority have been in the country for a long time so they knew how important the FA Cup is for the country and the club. I’ve been lucky to play in different countries, and the cup games are taken more seriously in this country than anywhere I have been.
“[Results] are always harsh because results are important in our industry, so the pressure [on Southampton] is really big. We have to manage and deal with it.
“Look at the last four or five games they played, look at the quality of the games they played. Some of those they deserve more than nothing. The result doesn’t reflect the quality of the games they played.
“This is [an all] Premier League game so we have to be really concentrated, determined and play with intensity to win the game.”
With the January transfer window open, Vieira discussed Jack Butland’s loan move to Manchester United.
“For us, we knew that we had three really good goalkeepers,” he said. “Jack was one of them. Sometimes players want to have more time on the field than you can promise.
“In the end, it’s a really good move for Jack. The last couple of years I worked him he has been a real professional and here at the club we wish him all the best.”
Vieira also took the time to pay tribute to former Chelsea, Juventus and Italy striker Gianluca Vialli, who passed away this morning at the age of 58.
“As a person, I think we can all agree what a nice guy he was,” he said. “A real gentleman. I had the chance to meet him off the field and he was always kind, always open for a conversation.
“He was a true gentleman.”