Aymar, a seven-time player of the year and widely considered to be the greatest female player of all time, led Argentina to a 2-1 victory against Britain on Wednesday. Her next, and supposedly last, match will be on her 35th birthday.
"It's going to be a classic," Argentina coach Carlos Retegui said. "Argentina has played Netherlands many times and (the teams have) set the standard of hockey for the past few years. I hope we see the best match in history."
Aymar helped Argentina win a silver at the 2000 Sydney Games, and bronze in Athens and Beijing.
"I'm just really grateful for life giving me the opportunity to play in more Olympic Games," she said.
The Dutch are the top-ranked team in the world, and the Argentines are right behind at No. 2. The South Americans also are the defending World Cup and Champions Trophy winners.
Argentina negated the home-field advantage early in the match when Noel Barrionuevo converted the only penalty corner of the first half in the fifth minute.
Four minutes before halftime, Carla Rebecchi collided with Britain goalkeeper Elizabeth Storry on the left baseline but she somehow kept the ball alive, dragged it around Storry's stick, fell forward and hooked it inside the left post.
Britain rebounded in the second half but Helen Richardson blew a free shot at goal in the 55th. She made up for the miss by passing to Alex Danson to score in the 64th, setting up a tense finish with Prince William's wife Kate Middleton looking on.
"Usually, I am the nervous type, but I had a good feeling I could do it," Hoog said. "I am very, very happy and relieved. It was a hard game and I am exhausted."
The Dutch twice came from a goal down to make it 2-2 at the end of regulation. Neither team scored in 15 minutes of extra time, forcing the shootout.
The Kiwis will play Britain for the bronze medal.
Keller, the first woman to play in five Olympics and Germany's flag bearer in the opening ceremony, set up two goals and was involved in a third.
"On the one side I am very sad because it's my last game," Keller said. "On the other side I am happy that we had a good end. I now have a new life."