Brendan Rodgers believes Leicester's tarnished trio can become heroes again after their coronavirus breach.
They were dropped for last weekend's 3-2 defeat at West Ham as punishment for attending a party at Perez's house following the Foxes' Premier League defeat to Manchester City.
Leicester are aiming to reach the FA Cup final for the first time since 1969 and Rodgers believes the players can restore their damaged reputations on the pitch.
"That is what they are very determined to do," he said. "These guys have made a great contribution for us, we are also in the position we are because of them.
"They made a mistake and in football there will be a choice again, at some point in their careers, and hopefully they'll make a better choice.
"We always have to look forward and it's in the past. The best way they can do that as a player is by their actions on the field.
"It's a really exciting period and they come in and are available. They know for the rest of the season they have to have that level of focus and commitment to achieve what it is we want to.
"We dealt with it last week when they trained separately and they understood the consequences. We had a meeting at the beginning of the week and we accept their apologies. They were sincere and knew they'd made a mistake.
"The team is based on pride and behavioural expectations and they fell below that."
It is the Foxes' first FA Cup semi final in 39 years, after they beat Manchester United in the quarter-finals, and Rodgers underlined the importance of keeping calm.
"In these moments that ability to have that self control is very important," he said. "When it counts most is when you are under pressure.
"We want to get into the final and we can only do that with performing well. If you overthink it or get nervous it can immobilise you.
"You stay calm, give clarity to the team and then arrive and look to play your game. We can't control what Southampton bring but we can control what we do."
Caglar Soyuncu is available after returning from Turkey having tested positive for Covid-19 while on international duty.
The game is also due to have 4,000 fans watching as a pilot event to trial the return of large crowds to UK venues amid the pandemic.
Rodgers added: "The players have done tremendously well to be so competitive (without fans). To have 4,000, it's a start of getting people back into stadiums and we'll look forward to seeing them there."