LONDON (Reuters) - Injured Gabriel Martinelli missed training ahead of Arsenal's Champions League last-16 return leg against Porto at the Emirates Stadium on Tuesday but manager Mikel Arteta refused to rule out forward's availability for the clash.

Martinelli sat out Arsenal's 2-1 win over Brentford in the Premier League on Saturday after the Brazil forward was substituted during last Monday's 6-0 victory at Sheffield United, having suffered a cut to his foot.