#2 Fernando Morientes' disallowed goal: Spain vs South Korea (2002)

The 2002 World Cup was a tournament of many firsts. It was the first time the quadrennial tournament was being held in Asia as Korea and Japan co-hosted it. It was also the first time an Asian team reached the semi-finals - thanks to some questionable officiating.
Spain met South Korea in the quarter-final after a controversial result saw the Asian side beat Italy in extra-time in the Round of 16 with Italian suggesting a conspiracy to eliminate the Azzurri. The quarter-final was no better as La Furia Roja suffered at the hands of the match officials this time.
Ivan Helguera's header was first chalked off after the referee spotted a lot of shirt-pulling in the box. While many think the goal should have stood, replays showed he did indeed tug the defender's shirt before finding the target.
However, it was a second disallowed goal that caused a lot of consternation. Spanish right winger Joaquin had been running that flank ragged and managed to put in a cross after getting to the goal line.
Fernando Morientes headed the ball past the goalkeeper at the far post but before he could celebrate, the linesman had put up his flag, claiming the ball had gone out of play when Joaquin crossed it.
"What happened here was robbery." - Ivan Helguera (who had to be restrained from the referee)
Replays are inconclusive as there was no angle available with the camera on the goal line. Close-up replays of when Joaquin crossed the ball do not show the ball going out when he made contact.
Whether it crossed the line in the air or not is up for debate as it was curled back in by the then-Real Betis winger.
This is one instance where VAR would have been very helpful. Such borderline decisions require technology to determine whether the ball did cross the line entirely. Even if a millimetre of the ball was 'within or on the line' it is still in play.
The incident occurs at 11:29 in the video.
Following the two dsiallowed goals, the match ended 0-0 and Spain would eventually go on to lose in the penalty shootout - with Joaquin missing the decisive spot-kick.