Mikel Arteta believes Gabriel Magalhaes missing a 91st-minute chance at FC Porto on Wednesday night changed the perspective of Arsenal’s Champions League last 16 tie. The Gunners had the chance to steal the lead in the closing stages of the first leg meeting in Portugal. But Gabriel spurned his chance to hand Arsenal the aggregate advantage ahead of Porto visiting Emirates Stadium on March 12. Instead, Galeno sealed the Dragoes a 1-0 lead. Galeno took full advantage of Gabriel Martinelli cheaply turning over possession in the final seconds to score a superb goal. Otavio easily intercepted Arse…