Roberto Carlos says his former side Real Madrid's chances in Tuesday night's Champions League last-16 second leg at Manchester United mostly hinge around one man - Cristiano Ronaldo.
Ronaldo has been in superb form recently, with 16 goals in 12 starts in 2013, including the equaliser against his former side in last month's 1-1 first leg at Madrid's Estadio Santiago Bernabeu, while his attacking colleagues Karim Benzema and Gonzalo Higuain have struggled for goals.
Ex-Brazil international Carlos, now sporting director at Russian club Anzhi Makhachkala, told Spanish radio show Al Primer Toque on Monday evening that if Ronaldo did not perform at Old Trafford then Madrid would find it difficult to progress.
"At the moment we are seeing Cristiano making the difference," Carlos said. "He stands out no matter who we are playing. He is doing everything to deserve the Ballon D'Or next year as the best player in the world.
"It is not like Barca with Xavi [Hernandez], [Andres] Iniesta or [Carles] Puyol. Madrid lives by Cristiano, Madrid breathes Cristiano, and if Cristiano is not on form tomorrow (on Tuesday) then Madrid will suffer even more."
Carlos said he had been impressed by the tactical and physical performance of Sir Alex Ferguson's side at the Bernabeu, but he nevertheless expected Madrid to make it through to the quarter-finals.
"Madrid can play well, I am sure of that," he said. "The big difficulty is that the game is at Old Trafford but Madrid can go through. We thought that at the Bernabeu Madrid would put three past 'El Manchester'.
"It will be a very difficult game, more difficult than the games against Barcelona. The English position themselves very well on the field, they are focused for the 90 minutes. El Manchester is a very dangerous team."
Blancos boss Jose Mourinho would also have a key role to play in the game, Carlos said. "Mourinho can decide games on his own," he added. "With his experience, his character. Often people do not realise that. Mourinho could determine things, with the 11 who play and the changes he makes. Mourinho will be very important for Madrid to go through."
Carlos, who played at Old Trafford as Madrid progressed in both the 1999-00 and 2002-03 Champions League competitions, said the 'galacticos' team of Zinedine Zidane, Luis Figo, Raul and the Brazilian Ronaldo had been a joy to play in.
"In that time it was very easy to play, we had players of such a high level, although I am not saying we do not have that now," he said. "But just one look and we knew how to play together. We enjoyed training."
Asked about his fellow Brazilian left-back Marcelo, who has been dropped recently by Mourinho having not returned from a broken foot in good shape, Carlos accepted Fabio Coentrao was the better option to play at the moment.
"Marcelo is a little bit overweight, but he will recover," he said. "If Coentrao plays he will do good work."