After 120 minutes of play, both Argentina and Netherlands failed to score. This resulted in the match to be decided on spot kicks. Argentina won 4-2 to set up a title clash with Germany on July 13.
Romero came in for huge praise after stopping two kicks in the shoot-out. And he was thanking the Dutch coach Van Gaal for the efforts.
The ball-stopper learnt the trade under Van Gaal when he was at AZ Alkmaar club in Netherlands. He spent two years under the manager.
"I taught Romero how to stop penalties, so that hurts," Van Gaal was quoted as saying in the media.
"We were the club to bring him to Europe. He was a big talent, and someone who has the qualities to do that," he added.
The 62-year-old Van Gaal had signed Romero from Racing Club in Buenos Aires to AZ in 2007.
After the game, Romero went and thanked his former coach. "I went to the dressing room to thank him. He is someone who helped me a lot when I arrived in the Netherlands, in a completely different country, with different customs.
"At the beginning I didn't speak a word, and he spoke Spanish and he helped me a lot," Romero said.