Krul was only brought onto the pitch in the last minute of extra time to take part in the shootout and Van Gaal has revealed that he did not tell Cillessen about the substitution beforehand.
"There is no question about who will start next game, it will be Cillessen. But we felt Krul was the better choice here," Van Gaal told reporters.
"We told Krul that he would be a possibility for the penalties, but we didn't tell Cillessen, as we didn't want to ruin his preparation.
"We have practised penalties, I believe when you're used to a certain shot you'll be more comfortable taking that shot."
The Netherlands and Argentina will meet at the Arena Corinthians in Sao Paulo next Wednesday for a place in the World Cup final.