Demichelis played with Aguero for club and country.
He told mancity.com: "Sergio has been scoring, goals, goals and goals since he was 15. Maybe at this point he's back in the spotlight because of the insane amount of goals he's scoring - he makes it look easy!
“I'm very happy for him, I love him, he's humble and a fantastic boy.
“After Gabriel Jesus' arrival, Sergio has being dealing so well with this healthy rivalry."
“Kun has everything, technically, physically and mentally. Day after day we're enjoying a better version of him which is fantastic not only for City but for Gabriel, too.
“I hope Sergio can keep breaking records, scoring goals and inspire City to many more trophies in the coming years.
“As a City fan, that will make me very happy!"