The Brazilian played with compatriots Willian and Luiz at Stamford Bridge before joining Shanghai SIPG in 2017.
Still only 29, Oscar has said his former teammates tried to bring him back to London this summer.
"They called me, they had to call me, because we have good communication, Oscar told Fox Sports Brasil. "Sometimes I talk to them.
"They said 'come to Arsenal, come here'. But for me it's a little more difficult. I have a contract with Shanghai, it's a little more difficult to leave.
"The most important thing is to be happy, regardless of the place. So I hope they are happy there."