Arsenal have sanctioned another exit this summer as midfielder Fabio Vieira is set to return to his former club Porto on loan. Emile Smith Rowe has already left, whilst Eddie Nketiah is in talks with Crystal Palace over a move. Vieira and Smith Rowe’s exits could leave Arsenal light in midfield, but they are expected to confirm the arrival of Mikel Merino from Real Sociedad, whilst youngster Ethan Nwaneri is now set for a bigger role. The loan move for Vieira will be critical for his Arsenal future. He has made just five Premier League starts since joining from Porto two years ago, and has fal…