City hold a 2-1 advantage for the second-leg of this round 16 tie.
"I'm going to see the game tomorrow with my new City shirt and supporting City," the Spaniard told Post United.
"A percentage? When Madrid reaches the Champions League, they may be in bad shape, but it's their competition. But this time it is very difficult, I think it is 80/20 for City."
When asked who would win the tournament, he added: "It's not because I just signed for that team but City is very strong, scores many goals and is very important. There is Madrid, there is Atalanta who is also very strong, Barca, we already know how these teams are."