Jorge 'Topo' Lopez - who was covering the tournament for La Red Radio - died when a stolen vehicle involved in a police chase collided into the taxi he was travelling back to his hotel in.
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The 38-year-old previously worked in Barcelona for Sport newspaper, where he became one of Messi's favorite journalists, and the 27-year-old paid tribute to him after the penalty shootout victory sealed a place in the final.
The Barcelona star wrote on Facebook: "I'm sending a big, big hug to the whole of Argentina and a souvenir to Jorge 'Topo' Lopez, this victory is especially also for you, my friend. A big hug to the family and lots of encouragement."
A dull semifinal saw the game locked at 0-0 at the end of extra time, with Argentina goalkeeper Sergio Romero emerging as the hero after saving penalties from Ron Vlaar and Wesley Sneijder.
Argentina will face Germany in the final on Sunday, and Messi struggled to contain his emotions after the game.
"I've had to do doping tests so I can't be in the locker room," he added. "I feel proud to be part of this squad. What a phenomenon we are involved in, let's enjoy, we have one more step."