The 18-year-old striker came off the bench in the second half to score another goal as the Red Devils defeated Northampton Town 3-1 in the third round of the EFL Cup at Sixfields Stadium.
Rashford has been in and out of United's starting XI in recent weeks but former club captain Neville feels Jose Mourinho has to start the talented attacker in the weekend's Premier League clash with reigning champions Leicester City.
Neville also believes Rashford can form a very deadly partnership with United star Zlatan Ibrahimovic.
"This kid is special," said Neville on Sky Sports.
"He has to start [against Leicester] - when a young lad is in such good form you've got to let them fly. You've just got pick him.
"It puts others under pressure, but this kid is special and he's scoring goals.
"The biggest quality he's got is his temperament. To play for Manchester United is not easy, especially at a young age.
"He's making it look easy - he's getting quicker, he's getting stronger and the relationship between him and Zlatan Ibrahimovic is going to be special."