BARCELONA: Real Madrid face Paris St Germain on Wednesday in the Champions League and it could be a match which defines their season.

Although third-placed Madrid crushed Real Sociedad 5-2 on Saturday at the Bernabeu, they still trail leaders Barcelona by 16 points and have no hope of defending their league title.

Coach Zinedine Zidane's future could depend on a good result in the last-16 first leg and the coach was relieved to see Cristiano Ronaldo hit his best form against Real Sociedad.

The Portuguese forward scored a hat-trick to reach seven league goals in his last four matches, turning his form around after a troubled start to the season.

Ronaldo netted four goals in his first 14 league matches, his poor form one of the reasons Barcelona were able to leave Madrid in the wake during the first half of the season.

"We are happy (with Ronaldo)," Zidane told reporters. "On Friday they asked me if I was worried about him not scoring goals and he scored three."

Last season Ronaldo converted into a centre-forward in a classic No. 9 mould from his previous role as a winger, helping the side retain the Champions League by scoring crucial hat-tricks against Bayern Munich and Atletico Madrid as well as a brace in the final against Juventus.

He was back to his clinical best against Real Sociedad after missing chances last weekend in a 2-2 draw against Levante, putting the final touch on an excellent team move in the first half and heading home from a corner.

Ronaldo's third goal exhibited his pure poacher's instinct, alert to fire home the rebound after Gareth Bale's shot was blocked by Geronimo Rulli.

As Ronaldo excelled, French striker Karim Benzema failed to break a league scoring drought which now stands at seven games and some supporters at the Bernabeu whistled him.

"I don't know why they are doing it," said Zidane. "They can do what they want. Karim had chances but for him the most important thing is the next game and changing his run."