Former Barcelona forward Rivaldo believes Real Madrid were taught a footballing lesson by Paris Saint-Germain in the Champions League and believes Zinedine Zidane may have to spend big again in January.
Los Blancos were beaten 3-0 by their Ligue 1 opponents in their Champions League group-stage opener on Tuesday, with two goals from Angel Di Maria and one from Thomas Meunier securing a 3-0 win for the Parisians.
To add to the misery for Zinedine Zidane's side, they failed to register a shot on target over the 90 minutes, while they also had two goals disallowed.
And Rivaldo, who spent five years at Madrid's great Liga rivals Barcelona, believes PSG taught their opponents a lesson at the Parc des Princes and thinks Zidane may be forced into signing more players in the January window.
He told Betfair: "Zidane has a lot of work to do to get his team back to what it was when they won three consecutive Champions League titles. But Madrid always are always a prize scalp for opponents, after winning so many titles in the past, so they need to give everything they have in every match.
"On the other hand, PSG were excellent in Paris with all their players performing well. It was a football lesson and if they follow this performance pattern, they should be considered favourites to win the Champions League.
"Yes, Madrid also had their absences in this match, and Sergio Ramos' leadership was missed on the pitch, but their midfield also had important absences and when you don't have enough players to replace others in the same quality things can get nasty.
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"Depending on how Madrid do between now and December, I believe Zidane might be forced to go to the market in January in order to bring one or two big players to the team."
Barca, meanwhile, kicked off their Champions League campaign with a 0-0 draw away at Dortmund, with Marc-Andre ter Stegen proving the hero as he saved a Marco Reus penalty.
And Rivaldo was full of praise for the German goalkeeper and believes he is proving that he is one of the world's best.
He added: "We cannot deny that Barcelona had a bad night against Dortmund and could easily have lost the match, but they had an inspired goalkeeper. Ter Stegen simply sealed their goal, making big saves and even stopping a penalty from Reus.
"The German is one of the best goalkeepers in the world, as he's strong between the posts and with his feet. His team-mates have no problems in passing him the ball as they know he is strong in that department, and even the opposing attackers don't press too much as they know he won't make mistakes.
"Ter Stegen transmits confidence to his team-mates and that's vital. He has been a little forgotten by Joachim Low in the German national team, but we should notice that Manuel Neuer is another big goalkeeper.
"I think Ter Stegen should focus on his daily work at Barcelona and producing solid performances, waiting for his opportunity at Die Mannschaft, which should come soon."