The Frenchman has become one of Europe’s most sought after centre-backs in recent times, with his commanding displays alerting the likes of Barcelona and Manchester City.
But, the Blues are believed to be at the very front of the queue, with Jose Mourinho desperate to land a top class enforcer to bolster his backline.
‘The Special One’ has been linked with a release clause-triggering £40m bid for the 22-year-old – an offer that would leave the Portuguese champions powerless to resist.
But, Porto are keen to keep Mangala and are set to offer him a pay rise to turn his back on a potential Premier league switch.
The Estadio do Dragao-based outfit have developed a reputation for nurturing talented players before selling them for huge fees, a move that has been employed with Radamel Falcao and Hulk in recent years.
Mangala only joined Porto from Standard Liege in 2011, but has been linked with a switch to one of Europe’s top leagues for some time.
As well as Chelsea and City, Manchester United are also watching the situation.