Former Middlesbrough midfielder Robbie Mustoe believes that Kai Havertz is now hitting his stride at Arsenal. Kai Havertz now looks to have finally settled into this Arsenal side. The German looked desperately short on confidence when he arrived at the Emirates Stadium from Chelsea in the recent summer transfer window. Havertz came in for plenty of criticism in the early days of his Arsenal career, as he struggled to adapt to Mikel Arteta’s tactical instructions and his £65 million price tag was called into question. In recent weeks, though, the 24-year-old has seemed far more assured of his r…