Russell Martin knows he has his work cut out to keep Southampton in the Premier League this season following promotion. Southampton have made eight first-team signings already this summer to help with that task, but Russell Martin knows more quality is needed in attack. As things stand, the only attacker that has arrived at Southampton this summer is Ben Brereton Diaz after the forward completed a £7 million move from Villarreal. The defence has been addressed, whilst Flynn Downes and Adam Lallana have signed in midfield; although Lallana did not feature once in pre-season due to injury. The f…