Arsenal legend, Paul Merson has warned defenders William Saliba and Gabriel Magalhaes ahead of their Premier League clash with Manchester City this weekend . Man City will tackle Arsenal at the Etihad Stadium on Sunday. However, Merson warned Saliba and Gabriel not to fall asleep when marking Man City striker Erling Haaland or else the Norwegian will score. “Gabriel and [William] Saliba will want to play against Haaland, someone who is going to go right up against them and wants a battle,” Merson said to Sky Sports. “They fall asleep then Haaland scores and that is the end of the game.” Haalan…