United’s hopes of a trophy this season and European football next season – vital for their financial issues – now rest on winning the Europa League.
Clubs were allowed to add three new players to their European squads by the Uefa deadline on 6 February before the start of the knockout round.
United added January signings Patrick Dorgu and 18-year-old Ayden Heaven, specifically to boost Ruben Amorim’s first-team squad.
But at that point Amorim was not considering Obi as a senior player and said the forward was someone who might get an opportunity later in the season.
In addition to increase to 25 ‘A’ list players, clubs can add players to their ‘B’ list to play in Uefa competitions at any point up to 2300 GMT the day before a game.
‘B’ list players are anyone who has been able to play for the club in question either for two continuous years from a player’s 15th birthday or for two out of three years if the player has spent time at another club on loan.
Obi does not meet the criteria as he only joined United from Arsenal in October.
Other youngsters available for Thursday’s game are Harry Amass, Louis Jackson, Habeeb Ogunneye, Jack Fletcher and Jayce Fitzgerald.
