The towering Krul replaced first-choice keeper Jasper Cillessen specifically for the shootout in Salvador after the teams finished extra time deadlocked at 0-0.
The 26-year-old vindicated his coach's unorthodox substitution when he saved spot-kicks from Bryan Ruiz and Michael Umana to give the Dutch a 4-3 shootout victory and a place in the semi-finals against Argentina.
But he also came under heavy criticism on social media for his intimidating tactics against the Costa Rican penalty takers, staring them down and yelling at them before they took their shots.
Asked whether he had overstepped the line of good sportsmanship, a defiant Krul said he had nothing to apologise for.
"I don't think I've done anything wrong," he told a news conference at his team's training ground in Rio on Sunday.
"I didn't shout anything nasty at them. I just told them that I knew where they were going. I'm trying obviously to get in their heads and it worked yesterday.
"It's a way of trying to psyche them out. Obviously they are under massive pressure, I'm under massive pressure as well so I used everything in my power to make it happen and luckily enough, happy enough it happened."
Krul, who has saved just two of 20 penalties he faced with his club side Newcastle, said the mind games had begun even before he stood on the line to try and save the first spot-kick.
Costa Rica had made the quarter-finals for the first time by beating Greece on penalties but Krul said he knew they were rattled as soon as they saw him warming up.
"I definitely think it had an impact, when I started my warm-up their whole bench was confused," he said.
"If you see their manager's face when I came on, he was looking over at our manager, his face was priceless. It was definitely one of those fantastic moves."
Netherlands coach Louis van Gaal, a renowned master tactician, had been hatching the plan for some time.
But he kept it such a secret that he did not even tell Cillessen and only let Krul know about it on the bus to the stadium but told him to keep it under wraps.
"The manager and the goalie coach told me before the game that if we had a substitution left there was a possibility that they may use me in the penalty shootout," Krul said.
"So obviously for me the whole game I was watching it with a different view because I knew the possibility was there.
"We have a plan before every game and I have my own style and I think it works. I'm over the moon that I saved two penalties."
Cillessen was initially disappointed at being hauled off before the shootout after keeping a clean sheet but was among the first to congratulate his understudy when the game ended.
"I didn't know anything about it beforehand so for me it was a big surprise," Cillessen said.
"I wanted to play everything. I wanted to play the penalty shootout as well but the coach made a decision that Tim was better than me and I had to accept it."
Krul accepted that Cillessen remained the team's first-choice and would not give away any more secrets about what the Dutch might have in store to stop Argentina captain Lionel Messi.
"They (Argentina) are a fantastic team. They are in the semi-finals so you have to be fantastic team to be there," Krul said.
"But we are a fantastic team as well and I think that we can be really confident with what we've shown and the players we've got.
"We're are really fit, I think we're fitter than most teams at the World Cup and we can be confident it should be a fantastic game.
"Hopefully we won't need to go to penalties against Argentina and we will get the job done in 90 minutes."
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- Jasper Cillessen