Newcastle United suffered an embarrassing FA Cup defeat at the Kassam Stadium this afternoon.
League One club Oxford United comfortably beat a weakened side 3-0 in a fourth-round tie.
Aleksandar Mitrovic, back from injury, had a second-half penalty saved in the game.
Goals from Kane Hemmings, Curtis Nelson and Toni Martinez put Oxford into the fifth round of the competition.
United manager Benitez had made nine changes for the tie ahead of Championship home games against Queens Park Rangers and Derby County,
And Oxford had the better start at a sold-out Kassam Stadium, where Mitrovic forced two first-half saves from Simon Eastwood.
But Hemmings seized on a loose ball from a corner to put the home side ahead early in the second half.
Mitrovic had a weak penalty saved by Eastwood after he was brought down by Phil Edwards.
And Nelson and Martinez netted late goals to ensure the passage of Michael Appleton's side into the next round.
NEWCASTLE UNITED: Sels; Good, Hanley, Haidara (Ritchie, 77); Gamez, Hayden, Barlaser, El-Mhanni (Gouffran 68), Lazaar; Perez, Mitrovic. Subs not used: Elliot, Dummett, Lascelles, Shelvey, Yedlin.
OXFORD UNITED: Eastwood, Skarz, Lundstram, Nelson, Maguire (Martinez, 70), Hemmings (Sercombe, 83), Edwards, Hall, Ledson, Johnson, Dunkley. Subs not used: Agboola, Macdonald, Ruffels, Rothwell, Raglan.
Goals: Hemmings 47, Nelson 79, Martinez 87
Booking: Hemmings 57
Referee: David Coote (Nottinghamshire)
Attendance: 11,810 (1,787 Newcastle)