Arsenal haven’t been quick movers in this summer transfer window so far. The Gunners have made just one senior signing this summer in the shape of Riccardo Calafiori. However, Arsenal are about to make their second signing of the window. Indeed, Mikel Merino is set to join Arsenal. This deal has been in the pipeline for a little while now, but, as we all know, no deal is done until a contract is signed. Luckily, it sounds as though we’re now at that stage. READ MORE: David Ornstein shares what he’s heard about Arsenal signing Raheem Sterling from ChelseaMikel Merino is an Arsenal playerAccordi…