Mikel Arteta has rebuilt Arsenal into a title-challenging side since he became manager in 2019, but he could not have done it without the help of one man. When Unai Emery was sacked in November 2019, Arsenal were in crisis mode. The squad was ageing, results were dire, performances were even worse and there was chaos at boardroom level. Less than five years later, the club is operating with an excellent recruitment structure in place, and a top-quality young squad are all tied down to long-term contracts. Even if Arsenal fall just short of the Premier League title this season, the progress the…