Like Liverpool, beaten at home by Wolverhampton Wanderers on Saturday, the three beaten sides miscalculated in resting so many players ahead of league games in midweek and could have no complaints at going out of the competition.
Yet United went through, winning 4-0 despite making nine changes at home to Wigan Athletic, who are in the bottom three of the Championship.
Watford lost 1-0 to League One (third tier) side Millwall and Hull, FA Cup finalists three years ago, were humbled 4-1 by Championship (second tier) side Fulham after missing two late penalties.
Leeds, fourth in the Championship and giving greater priority to returning to the Premier League after a 13-year absence, lost 1-0 to Sutton United, who joined fellow fifth-tier National League club Lincoln City in the last 16.
It is the first time two non-League clubs have progressed that far since the competition was reorganised more than 90 years ago.