Arsecast contributor Phil Costa has shared his view on the performance that Gabriel Martinelli put in for Arsenal against Porto on Wednesday night. Gabriel Martinelli was far from his best as Arsenal slumped to a 1-0 defeat in their most recent Champions League clash. The Gunners were poor to a man as they were deservedly beaten at the Estadio do Dragao in this first-leg of their Champions League round of 16 tie. However, Martinelli was particularly off the pace in Portugal, considering the high standards he is known to be capable of reaching. He was poor on the ball, weak in his duels, and un…