Barcelona wary of red-hot Ronaldo in El Clasico
Ronaldo has hit form at just the right time, netting three in the 4-1 win at Ajax in the Champions League on Wednesday, that haul coming after his hat-trick in the 5-1 La Liga rout of Deportivo La Coruna last weekend.
The last time Real and Barcelona clashed in the league last April, Ronaldo scored the decisive goal at the Camp Nou as Madrid went on to win the league.
But this season Barcelona have begun with ominous intent to reclaim their crown with six straight victories.
Perhaps the result of basking in their own triumph, Jose Mourinho's side instead made a stuttering start with just one win from the first four games but since then they have clicked into gear and Ronaldo has looked more like his old self.
The Portuguese had looked moody and introspective, refusing to celebrate some goals with his team-mates and declaring himself unhappy but his winner against Manchester City in the Champions League last month showed his desire was back.
And now he is fully primed to face Barca after his successive hat-tricks.
"I am very happy with the way we are playing and the victory against Ajax gives us all plenty of confidence while for me personally to score three is vital for my own confidence," said Ronaldo.
"We will go to the Camp Nou which is a very difficult stadium but we have belief in our chances and that we can get a good result. Barca have a very strong side with strength in depth."
His teammate Xabi Alonso admitted that there is no margin for error.
"To win will be fantastic and lose, bad, there is no way of hiding the fact. We are aware of the difference in points and so obviously we are going out for the victory but we need to rest and prepare," he said.
Although Barca have a 100 per cent record they have had injury worries to deal with especially in defence.
And the bad news to come from their mid-week Champions League win over Benfica was that Carles Puyol will be out of action for up to two months with a dislocated elbow.
The talismanic defender was only just returning from a lengthy layoff and is now back in the treatment room along with fellow centre-half Gerard Pique, so it is likely that Javier Mascherano and Alex Song will line up in the heart of the defence on Sunday.
Elsewhere unbeaten duo Atletico Madrid and Malaga go head-to-head while high-flying Sevilla and Mallorca, both on 11 points, are against Celta Vigo and Granada respectively.
At the other end of the table the situation remains desperate for Espanyol who have just one point and they are now away to Valladolid while Athletic Bilbao and Osasuna immediately above them face each other.
Fixtures (all times GMT)
Celta Viga v Sevilla (1900)
Rayo Vallecano v Deportivo la Coruna (1400), Valladolid v Espanyol (1600), Zaragoza v Getafe (1800), Real Betis v Real Sociedad (2000)
Levante v Valencia (1000), Mallorca v Granada (1400), Athletic Bilbao v Osasuna (1600), Barcelona v Real Madrid (1750), Atletico Madrid v Malaga (1930)