The Los Blancos defeated the Red Devils to win the UEFA Super Cup on Tuesday.
The winners of the UEFA Champions were superior to Manchester United and scored in each half of the game before the English side pulled one back.
Casemeiro registered the opener in the first half when he finished off, after he was put through by Dani Carvajal.
The Spanish giants doubled their lead in the second half when Isco rounded David De Gea, but Lukaku got the consolation goal for Manchester United when he scored from the rebound.