The Bluebirds go into the clash 1-0 behind following their defeat in the opening leg at Selhurst Park, but have won 13 of their 17 home games this term and will fancy their chances of turning the tables and securing a third visit to Wembley in five seasons.
Freedman has attempted to pile the pressure on the Welsh club by suggesting their supporters will be "scared stiff" of seeing their charges come up short again following their play-off defeats to Reading in the semi-finals last year and Blackpool in the 2010 final, as well as their 2008 FA Cup final loss to Portsmouth.
Mackay says he is unconcerned by his fellow Scot's comments, and has backed the Cardiff faithful to be their 12th man.
Mackay told a press conference: "As far as his comments are concerned I look after my own club, it is not my style to about other clubs. I have enough to be dealing with here, but, needless to say, part of the team talk is done.
"We are obviously excited. We are in the semi-finals of a cup, we are preparing properly but we are looking to enjoy it.
"We have done well in the Carling Cup this season, we have had some fantastic games and have all enjoyed it.
"We are 1-0 down at half-time so to speak, but we are going back to our stadium and it will be a full house and rocking like it was on Saturday.
"I was delighted with how the fans showed their passion and got behind the team on Saturday and I don't any difference tomorrow night. It will be a fantastic occasion but we need to play the game, not the occasion.
"The fans have been through it before but I can only talk about what I see and feel here, and I feel a confident stadium with people who desperately want the team to do well because they see the team care, they see a team playing with passion and they embrace that. That's why I feel they can be our 12th man back at Cardiff City Stadium."
With Cardiff flying high in the npower Championship and targeting promotion, Mackay played his strongest available side in Saturday's thrilling 3-2 victory over Portsmouth, which was sealed by Craig Conway's last-gasp strike.
Freedman, meanwhile, was able to rest the majority of his side, who lie firmly ensconced in mid-table.
But Mackay does not expect his side to suffer in comparison.
He said: "Everyone looks at their own situation and what their remit is, whether it is staying in the division, finishing in mid-table, the top 10, the top six or whatever it may be.
"But on Saturday I wanted to put a strong team out there, it was an important league game and we had to make sure it did not detract from this week.
"I have no doubt in the athleticism of my team to play Saturday and Tuesday like we have done in the league many times.
"If we had league games on Saturday and Tuesday I wouldn't rest nine players, I would play my team. We have a confidence in the ability of my team to run for 90-95 minutes or longer if it should be needed."
Mackay will wait before making a decision over the availability of Kevin McNaughton.
The Scot is currently recovering from the calf niggle that has kept him out of action since the first leg. Darcy Blake is set to continue in his place if he does not make it.
Striker Rudy Gestede is also coming back from an ankle problem, while Robert Earnshaw was named on the bench for Saturday's win over Portsmouth after a muscle strain.
Crystal Palace boss Dougie Freedman will recall a host of his key players when they look to defend a 1-0 lead.
Goalkeeper Julian Speroni, skipper Paddy McCarthy, fellow defenders Anthony Gardner and Nathaniel Clyne, midfielders Mile Jedinak, Kagisho Dikgacoi and Darren Ambrose, winger Wilfried Zaha and strikers Glenn Murray and Chris Martin were all rested for Saturday's 2-1 defeat at Blackpool.
Wideman Sean Scannell also returns from suspension and left-back Dean Moxey has recovered from a knee injury, but on-loan right-back Mustapha Dumbuya is cup-tied.
The virus which disrupted Palace's preparations for the first leg has cleared up so midfielder Jonathan Williams is the only injury absentee as he continues his recovery from a broken leg.
Cardiff have no new injury or suspension worries.
Trailing 1-0 following the first leg at Selhurst Park a fortnight ago, manager Malky Mackay has still got lingering doubts over defender Kevin McNaughton (calf) and striker Rudy Gestede (ankle).
However, other than the injured duo, Cardiff are at full strength to take on the visiting Eagles.
Darcy Blake is likely to continue in place of McNaughton if the Scot is unable to take his place on the right of defence and Mackay is not expected to make many changes to the team that saw off Portsmouth 3-2 in the Championship on Saturday.
Goalkeeper Tom Heaton has started five of Cardiff's six Carling Cup matches this term, however, and could be recalled in place of David Marshall.