The 25-year-old Egypt international was unable to travel to the Algarve with the rest of his team-mates, who play Celtic this evening, because of a problem with paperwork.

Boro have spent the last few days trying to resolve the matter to allow the former Tottenham frontman to meet up with manager Gareth Southgate and his squad.

But it could take up to a week for a visa to be issued, and that is a major disappointment for a player who returned for pre-season training in good shape after spending several weeks working with fitness coach Nick Allamby in his home city of Cairo following an injury-hit first campaign on Teesside.

Mido said: "I would like Boro supporters to know why I am not in the team for this evening's game in Portugal against Celtic.

"There have been ongoing problems regarding my visa, which I hope to have sorted shortly.

"It could be that the Portuguese embassy require up to a week to amend this situation, thus preventing my ability to travel to Portugal in the very immediate future."

Boro play their second game on Thursday evening, when they will meet Vitoria Guimares at the Estadio Algarve in Faro.