Fabregas rejoined the Catalan outfit from Arsenal in 2011 and scored an impressive 42 goals in 151 games for Barca.
The Spaniard moved to Chelsea this summer, but Tello has said that the midfielder left "through the back door".
"Cesc didn't leave the club as he deserved to," Tello told Sport.
"He left through the back door. Cesc was a fantastic player and you only have to look at the goals he scored and the assists he provided in his time at Barcelona. I suppose he will now be hurting because it was his dream to be a success there."
Tello is currently on loan from Barcelona at Porto.