The Championship club travel to north London hoping for a repeat of last year when Simon Grayson's men stunned the then Premier League champions Manchester United with a 1-0 victory.
United's first visit to the Emirates Stadium is one of six ties that pit Yorkshire sides against top-flight opposition and McCormack claims the Elland Road club could not have been handed a tougher assignment than taking on Arsene Wenger's men.
The 24-year-old, who moved to West Yorkshire last August, was in the Cardiff City side thrashed 4-0 in a fourth round replay by the Gunners in 2009 so speaks from personal experience of the qualities that Leeds will have to counter in front of the ITV cameras this lunchtime.
McCormack said: "A lot of the lads played against Manchester United last season and that should stand them in good stead. But I personally feel going to the Emirates is different to going to Old Trafford.
"The night I went to Arsenal with Cardiff (in 2009) was horrific, I don't think we managed even one shot. It is so difficult to get the ball off Arsenal. But we will go there and give it a go.
"I would imagine they will change their side but that will mean guys like (Andrei) Arshavin coming in. He is world class and in a different league but we want to test ourselves against the best.
"We have a good squad, you could see that in midweek at Cardiff by (top scorer Luciano) Becchio being a substitute and (Davide) Somma not even being on the bench. That is why I don't think we are under-achieving in the league.
"The Cup game will be a big occasion but the league is our priority. Despite that, I am sure the gaffer will say, 'This is the Cup so just let the occasion take care of itself'. We had been on a good run before losing to Cardiff and should not forget that."
Among the half-dozen Yorkshire clubs taking on Premier League opponents today are Sheffield United, who host Aston Villa, and Doncaster Rovers, who entertain Wolverhampton Wanderers at the Keepmoat Stadium.
Barnsley, meanwhile, travel to West Ham United, Hull City host Wigan Athletic, while non-League York City face the task of bridging a five-division gap against Bolton at the Reebok Stadium.
It is at Arsenal, however, where millions will tune in to see if Leeds can repeat the Cup heroics of last season.
One man who believes the Elland Road club have the quality to cause problems for the Premier League giants is manager Grayson, who has vowed not to follow the lead of Manchester City's Roberto Mancini after the Italian sent out a defensive-minded side that ground out a goalless draw at the Emirates Stadium on Wednesday night.
Grayson said: "No, we won't be doing that. We will try and play how we play on a regular basis. I want us to score goals. That is my philosophy.
"I don't want to sacrifice the attacking side of it with a defensive approach.
"We have players who I feel can hurt any team that we play against. We will have a go. We have nothing to lose. There have been teams who went there and got results by defending and others who did so by taking the game to Arsenal.
"Before every game, we do a presentation of all the strengths and weaknesses of the opposition. I am not sure how long we will spend on their weaknesses, to be honest. And there will be plenty of strengths.
"But Arsenal have deficiencies, like every team in the world. They are only human and do make mistakes, which we have to capitalise on.
"We have a talented group of players who can create chances. We showed that last season, as we have again this year against the top teams in the Championship. We know we are going up a level now but I won't tell the players to do anything different to what they do week in, week out.
"I don't want to sit back and invite pressure. If we are going to lose, we will go down fighting."
Leeds proved to have a liking for Premier opposition last season with the win at Old Trafford being followed by United holding Spurs to a 2-2 draw at White Hart Lane in the fourth round before bowing out after a replay.
Grayson, whose side also lost 1-0 to Liverpool in the Carling Cup last term, said: "I would back this squad to win a lot of matches in the Premier League if we were in there now. We would also lose a lot, too.
"We are a long way off the Premier League but this weekend is a test for us to see where we are at. We have nothing to lose. Cup games are a one-off and, hopefully, we can cause a shock.
"All I ask of my players is that they finish the game having no regrets.
"Ninety per cent of them will have never been to the Emirates before, never mind played there."
Wenger is likely to make changes from the side held at home by City in midweek but Grayson added: "Like Manchester United last year, the changes will all be internationals."