By Jamie Spencer Arsenal are reported to have agreed a deal with Porto to loan Fabio Vieira back to the Primeira Liga side, two years after arriving in north London. Vieira has largely been a fringe player at Arsenal, spending much of last season on the bench, both before and after a groin injury ruled him out for a couple of months. Playing time could be further limited by the impending arrival of Mikel Merino from Real Sociedad and the continued emergence of Ethan Nwaneri from the academy. The Athletic writes that Vieira will return to former club Porto on loan and will not be part of the sq…