The Sky Blues were close to tying up moves for the pair in January, but baulked at the Portuguese giants’ valuations of their men on deadline day.
Yet they have since been keeping tabs on both, and are ready to re-visit Porto with a new £41m offer.
Centre-back Mangala is seen as the top target by Manuel Pellegrini, who is desperate to provide captain Vincent Kompany with an able partner at the back.
The commanding Belgian has been placed alongside Martin Demichelis for many of the recent games, during which time the veteran Argentine has appeared unconvincing.
Mangala, 23, is rated at around £29m on the back of some impressive displays over the course of the past two seasons.
Fernando is also on City’s agenda, with a £12.4m raid being lined up.
The Brazilian midfielder only penned a new contract at the Estadio do Dragao in February, but it is understood that this was only a manoeuvre to prevent him leaving on a free when his previous deal expired – which would have been in a few months’ time.
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