Last year's beaten finalists were paired with the North London outfit in this year's edition of the tournament, along with Napoli and Marseille.
Weidenfeller believes that Arsenal's deadline acquisition of the Real Madrid ace will make for a fiercely competitive group.
He told Bild: "Arsenal have gained enormous quality by signing Ozil.
"Napoli have also strengthened and I am sure it will be a great challenge."
Arsene Wenger's men welcome the German giants to the Emirates Stadium on October 22.