Mendes is well-known to the North London outfit, representing manager Jose Mourinho, an arrangement that has seen him conduct a number of deals with the club in the past.
And it could prove so again in the not-too-distant future, with speculation that the Blues view Mangala as a potential long-term replacement for skipper John Terry.
Any potential deal is far from done, however, with the 22-year-old on the radar of a number of Europe’s top clubs, including Manchester City.
City were said to be trying to secure the signature of the French international in the summer but instead opted to move for cut-price Martin Demichelis from Atletico Madrid.
Now it is thought that Mourinho could swoop for Mangala in January, assuming Chelsea owner Roman Abramovich is prepared to meet the £40m buyout clause in the Porto enforcer’s contract.