Karanka said: "Real Madrid are coming into the match in good form, and not because of (last night's) result.
"Apart from the match against Granada, the team has been showing good things throughout January. (Against Sevilla) we played well and have given a bit of a rest to key players and the match comes at a good time for us."
On the extra day's rest, Karanka said: "We've proven it ourselves - it does show.
"They have a bit of a cushion (at the top of the Barclays Premier League) and I'm sure they'll be making rotations and resting important players."