With Zlatan Ibrahimovic, Anthony Martial and Wayne Rooney all unavailable, the Red Devils were in danger of having to get creative in their selection – with Marouane Fellaini expected to step in.
Rashford has, however, recovered in time to link up with his team-mates in west London and offer a more natural option in a striking berth.
A place at Wembley in the last four is up for grabs at Stamford Bridge, with United boss Jose Mourinho looking to prevent his former employers from taking that step.
The Portuguese has already guided his side to domestic success in the EFL Cup this season, while opposite number Antonio Conte is chasing down a Premier League and FA Cup double.
Chelsea are in the fortunate position of being able to name a strong XI, with Nemanja Matic back into their midfield while Cesc Fabregas drops to the bench.
United have gone for three at the back, with Ashley Young and Henrikh Mkhitaryan offering the attacking support to Rashford up top.
Chelsea team: Courtois; Azpilicueta, David Luiz, Cahill; Moses, Kante, Matic, Alonso; Willian, Diego Costa, Hazard. Subs: Begovic, Terry, Zouma, Chalobah, Fabregas, Pedro, Batshuayi.
Man Utd team: De Gea; Jones, Smalling, Rojo; Valencia, Herrera, Pogba, Darmian; Young, Mkhitaryan, Rashford. Subs: Romero, Bailly, Blind, Carrick, Fellaini, Lingard, Mata.