Arsenal have lost rising starlet Chido Obi-Martin from their academy, and he has now joined a direct rival. Obi-Martin was a goal machine at under-18 level, breaking Folarin Balogun’s Arsenal record, but the striker stalled in contract talks after claiming that he wanted a clear pathway to first-team action. Arsenal offered him a sizeable deal, but Manchester United blew their offer out of the water financially, and the 16-year-old has now moved to Old Trafford. It is a blow for Arsenal to lose such a big talent, particularly after Mikel Arteta even held talks with the teenager over his pathwa…