Thohir has called on supporters to show their backing and belief in the team.
"It will be a great match against Napoli. There will be lots of Nerazzurri fans at the stadium and, together, we can play our part," Thohir has told Inter's official website.
"It will be a tough match but we are Inter and that's why our time will come on Sunday.
"It will be a chance to express, along with our supporters, the enthusiasm needed to build a great group, especially such a young one like ours.
"Inter is a part of me, it's a part of all of us: I will be the first to cheer on the team as a supporter on Sunday.
"We all need to be united in supporting Inter, we have to be the 12th man out there and make the difference.
"There's no other stadium in the world like San Siro. When the atmosphere really builds it becomes very intimidating for opponents.
"The Coach and team are expecting you all at the stadium on Sunday to bring Inter together. Forza Inter!"
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