Chelsea had scouts posted to see Benfica meet Academica on the weekend.
Record says Chelsea and Valencia were represented at the game, won 5-1 by Benfica.
Jonas struck twice in the rout.
In recent transfer windows, Chelsea have added David Luiz, Ramires and Nemanja Matic from Benfica.
Valencia, meanwhile, boast former Benfica stars Enzo Perez and Andre Gomes in Nuno's squad.
Reading also had scouts in attendance