The Manchester City striker missed the Albiceleste's victories over Switzerland and Belgium after limping out of their final group game against Nigeria with a muscle injury.
But he returned as a late-second-half substitute on Wednesday as Argentina beat Netherlands 4-2 on penalties to book a place in showdown with Germany and the 26-year-old is ready to put his injury woes behind him for what he describes as a "dream" World Cup final.
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Joachim Low's side thrashed Brazil 7-1 on Tuesday in a staggering match but the Argentina star does not believe that Germany will be overconfident heading into the final.
"Germany are always a tough team at the World Cup but we will continue to play our game," he added. "Argentina is Argentina. Germany also have a bit of respect for us."
Javier Mascherano also spoke of his pride at making it to the final, labelling his team's achievement "brilliant", and knows that it is a chance that may well only come once.
"We played a brilliant game, without any fear of anything," enthused the Barcelona man.
"We came into the game of our lives and now we will enjoy it because this is a once-in-a-lifetime opportunity.
"Hopefully we will be crowned champions on Sunday but, regardless of the outcome, I have no words to express how proud I am ... the goal was to be in the final."