Manchester United thought they were signing a Sanchez at the peak of his powers when he touched down from Arsenal back in January. Things have, however, gone sour just 10 months into his Old Trafford career. Manchester United have failed to coax the best from Sanchez during his time at the club so far. For all his brilliance at Arsenal, the 29-year-old has looked a shadow of his former self. Reports have linked the Gunners with a sensational move for a player who quit the club less than a year ago. And Sanchez may be tempted to swap Old Trafford for the Emirates for two reasons. 1 - Sanchez would be leading light at Arsenal.United signed the Chile international because they believed him to be the answer to their attacking troubles. The decision to give him their famous No 7 shirt also suggested he was primed to usurp Paul Pogba as club talisman. That has not happened, however. Jose Mourinho seems reluctant to let his star asset off the leash and, as a result, he has managed just three goals. Should he return to Arsenal, however, he would likely be their leading man.The Gunners’ current best players - Pierre-Emerick Aubameyang and Alexandre Lacazette - are still battling for consistency. Sanchez would, though, immediately become one of the first names on Unai Emery’s team sheet. 2 - Time is running out for Sanchez.A second reason the United man may consider a return is because he is approaching the latter stages of his career. And what better way to spend his final years at the club where he enjoyed his best spells?. At the moment, Express Sport understands Arsenal are yet to consider a Sanchez return. But with his United career continuing to go from bad to worse, a parting of the ways could be on the cards. Mourinho’s own future is thought to be key to his future.Should he go, then Sanchez will likely stay. But, with United counting to back their manager, it looks a saga primed to run for some time.