By Josh O’Brien Mikel Arteta has conceded transfer mistakes are “inevitable” when asked about Arsenal’s decision to pry Kai Havertz from Chelsea last summer. The Germany international cost the Gunners £65million and after an underwhelming start to life at the Emirates, Havertz has started to come into his own in recent weeks. Two goals against his former side in his last outing for Arsenal means the 24-year-old’s stock is considerably higher among the fanbase than it was in his first few months. Havertz could seal his place in the hearts of Arsenal supporters everywhere if he is back among the…