The France U21 international has attracted admiring glances from a host of top European clubs after a series of impressive performances in Portugal this season.
Jose Mourinho is believed to be a huge admirer of Mangala, and is planning to bring him to Stamford Bridge should he return to Chelsea this summer.
However, the Blues will face competition for the 22-year-old's signature with Manchester United also credited with an interest in his services, as David Moyes makes plans for his first signing as Manchester United manager.
Rated at around £17million, it will take a significant offer for Porto to sell their star defender, but it's thought that Serie 'A' champions Juventus are ready to meet his valuation.
With a number of different parties vying to sign Mangala, the Primera Liga club might look to set off a summer bidding war and look to gain as much money as possible before considering a replacement signing at the Estadio do Dragao.