At first, it appears that Barcelona midfielder de Jong grabs Madrid's star winger in the groin area. But the 22-year-old Brazilian holds his ground.
All looked like the typical fierce battle between the La Liga giants but it's Vini's headlock that tees up the yellow card.
The two rival players quickly shook hands and moved on afterward. But the 22-year-old carried on to get in the face of the referee, fortunate to avoid a red.
Meanwhile, Barcelona's teenage starlet Gavi escaped a yellow card after his foul on Eder Militao. The 18-year-old averages 12.3 fouls per yellow card — a curious escapee. But his accumulation sees him sitting out against Valencia on Sunday.
Franck Kessie nearly scored Barcelona's second in the 73rd minute but the ball took an unfortunate ricochet off the heel of teammate Ansu Fati.
The game finished 1-0 for Barcelona, without Lewandowski, Pedir, and Dembele. It's also Los Blancos first defeat at the Santiago Bernabeu in 11 months.
Real Madrid have not made it to the final of the Copa del Rey since they won it during the 2013/14 season. The two sides meet for the second leg on April 5 at Camp Nou, with Madrid looking to exact revenge.