Osasuna have proved tough opponents in recent times for Madrid.
Ramos admitted on his club's website: "It's always a difficult game, and much more with Osasuna going through a difficult time of it. Right now they are fighting to avoid dropping into the relegation places, but a hurt team is always more dangerous.
"(But) we all have to be very clear that we need to continue winning games.
"Unfortunately we don't depend on ourselves and we mustn't drop any more points. If we don't do that, the points difference (to Barca) will climb too much."