Mascherano lunged to block an Arjen Robben shot on the stroke of 90 minutes in their semi-final in Sao Paulo, denying the Dutchman a huge chance to send the Netherlands into Sunday's final.
The Barcelona stopper tracked Robben's run into the left side of the area, and stopped the Bayern Munich man's shot with the bottom of his boot, before Argentina went on to advance to the final via a 4-2 penalty shoot-out victory.
Mascherano said he feared the worst as Robben broke clear.
"It was terrible. I thought I'd slip, I thought I wouldn't make it, I thought he'd get ahead of me. I thought so many things," he said, in an interview with the Independent.
"But I did get there and it wasn't a goal."
Mascherano graciously credited his match-saving tackle down to Robben's decision to take an extra touch once in behind the Argentine defence.
"He played a great exchange with (Wesley) Sneijder but, because of that extra touch, he didn't quite hit it so early, it gave me the possibility, that extra split second," he said.
"The truth is there's not much doubt for me. I just threw myself into it.
"If I was a moment off, it was a penalty. There's no doubt.
"Anyone could have done that, I was lucky to get there.
"The team was lucky Robben took one more touch. To get to a final, you always need a bit of luck."
Mascherano said the squad have given their all, to be within one win of World Cup glory.
"We did the things we had to do. We have the tranquility of having given everything, of having performed like we had to," he said.
"That forms part of this group. It's been so many years but now our country, and our flag, are in the eyes of the world, returning to a World Cup final, the most important match of our careers.
"It's a delight, a delight that lifts your soul. It's something you can't explain, something I never imagined, but there we are."
