The Portuguese has fired warning notes to the Stamford Bridge side ahead of the clash between both sides
The Red Devils will visit Stamford Bridge on Sunday to lock horns with Blues following their energetic win against Villarreal on Tuesday night.
United are without a proper manager, with Micheal Carrick in charge as Caretaker manager after the sack of Ole Solskjaer.
Chelsea are in a better form and are looking to cause damage to United who are struggling to recover from their loss of points over the past weeks.
Having seen a severe down point, United will be hoping to find at least a draw against Chelsea who sit top of the Premier League table with highest goals scored and fewest conceded.
According to Cristiano Ronaldo, Chelsea should be wary of the match which they believe they can be the superior side over United.
Speaking to BBC, Ronaldo said; “They [Chelsea] are doing well, but we can see what will happen on Sunday.
“We are a team that are ready to win. We want to cause other teams damages and score many goals.
“We are hungry, especially at this point in time, maybe Chelsea will be tougher than we expect but we will be ready for any challenge.
“We are now in the knockout of the Champions League and are also looking if we can bring the trophy home to Manchester.
Chelsea will be fired up with the return of Romelu Lukaku who missed out their last games through injury.
Timo Werner is also back as he made an appearance against Juventus where he scored the last goal of the game.