Manchester United hung on for three important points in their pursuit of a top four finish after Casemiro was sent off for grabbing Crystal Palace's Will Hughes by the throat.
Amid a mass bust-up 20 minutes from time, replays caught the Brazilian raising his hands to the Palace midfielder, leading to referee Andre Marriner flashing the red card following a VAR consultation.
But United defended for their lives in the final 20 minutes, plus nine additional ones, despite Jeffrey Schlupp reducing the arrears.
It meant an early penalty by Bruno Fernandes and Marcus Rashford's second-half goal proved enough to extend United's cushion to Tottenham to six points.