The Brazil international left the Gunners last year for Greece.
"I have made so many friends at the Club I would describe it as a family for me. I am at Panathinaikos now but a part of me is still at Arsenal. It is a special club and there are so many special people.
"The players who have had the opportunity to play for Arsenal experience this atmosphere of a family club.
"Once they leave they always miss it and I'm sure it's like this for Arsène Wenger as well, it's why he's here doing this great job for a long time.
"I'm sure one day when he leaves the Club he will leave a great legacy for the Club."