The Reds have tweaked the UEFA B list ahead of the deadline for Thursday's round-of-16 second leg at Old Trafford.
The tie, finely poised at 1-1 following the first leg, kicks off at 20:00 GMT.
Tyler Fredricson and James Scanlon are the two names introduced, as they will hope to make the matchday squad for what promises to be a big occasion under the lights at the Theatre of Dreams.
Centre-back Fredricson captained our Under-19s in the UEFA Youth League and was an unused substitute for the Premier League contest at Tottenham Hotspur last month.
Scanlon is a full international for Gibraltar but has yet to be involved in a senior match for the Reds.