Fish, 18, trained with the first-team on Tuesday and United are without suspended trio Harry Maguire, Luke Shaw and Scott McTominay. Eric Bailly tested positive for Covid-19 while on international duty with the Ivory Coast and is unlikely to start against Granada.
Fellow centre-back Phil Jones has not played since January 2020 and has been sidelined since June with a knee injury, while Teden Mengi is on loan at Derby County, so United lack cover at centre half. United can name 23 players in their Europa League matchday squads.
Manchester-born FIsh has started in 17 of the Under-23s’ 20 Premier League 2 matches this term and lined up in the recent FA Youth Cup defeat to Liverpool.
Anthony Elanga, who was added to the Europa League squad for last week’s first leg, could be back on the bench and so too could Shola Shoretire, who became United’s youngest European debutant against Real Sociedad in the round-of-32 first leg.
Ethan Galbraith is still listed in the United Europa League squad, which was last updated on Tuesday evening. United can add Fish to their ‘B list’ 24 hours before kick-off against Granada.
Under Uefa rules, a player may be registered on the B list if he is born on, or after, January 1 1999 and has been eligible to play for the club concerned for any uninterrupted period of two years since his 15th birthday. Hannibal Mejbri is ineligible for the B list as he only joined United in August 2019.
An issue with any U23 inclusions for the Granada tie is the United second string face City on Friday night, 23 hours after kick-off in the Europa League.
Possible United squad
De Gea, Henderson, Grant, Bishop, Wan-Bissaka, Williams, Lindelof, Tuanzebe, Fish, Telles, Matic, Fred, Pogba, Van de Beek, Fernandes, Mata, James, Amad, Greenwood, Rashford, Cavani, Elanga, Shoretire