Hosts Boro will head into the game as favourites, but manager Karanka is not taking anything for granted.
"They're a team with a very good manager,” the former Real Madrid defender told Gazettelive.co.uk. “He’s a good manager and his sides are always organised. I'm expecting a very tough team.”
"Leeds are a team who are always difficult to play,” added Karanka. “I have never beat them. I'm working in the way that I always work.
"I couldn't beat them the last four times but the team is now a lot different to the team who played them two years ago.
"I have to analyse them and beat them knowing their weaknesses and knowing their strengths.”
Middlesbrough are in very good form at the moment and are on course to a top-two finish in the Championship this season.
Boro are currently second in the league table with 17 points from eight matches, just three points behind leaders Brighton & Hove Albion.
Karanka’s side will head into Sunday’s match on the back of a 3-0 victory over Wolverhampton Wanderers at the Riverside Stadium in the third round of the League Cup.
Meanwhile, Leeds will head into the match on the back of a 2-1 victory over Milton Keynes Dones away from home in the Championship.
Uwe Rosler’s side are 11th in the league table at the moment with 11 points from eight matches, just a point behind sixth-place Reading.