Former Middlesbrough midfielder Robbie Mustoe has been blown away by the improvement he has witnessed in Arsenal star Kai Havertz in recent weeks. Kai Havertz now looks to have really found his feet at Arsenal. The German had a difficult start to life at the Emirates Stadium. He arrived in north London looking short on confidence and struggled to immediately get to grips with his tactical function in Mikel Arteta’s side. Havertz was heavily criticised in his first few months at Arsenal. However, in recent weeks, the 24-year-old has finally found his groove. In the absence of the injured Gabrie…