Argentina coach Michael Cheika said a weight of expectation would force his players to change their mentality going into next weekend's World Cup quarter-final against Wales.
Mateo Carreras scored a hat-trick as Los Pumas outscored Japan five tries to three in an enthralling final Pool D encounter in Nantes on Sunday.
The victory meant Argentina finished as runners-up behind pool winners England, but Japan return home after finishing in third position.
"We are where we want to be," Cheika said. "But we want to go further, we want to reach the semi-final and the final, that's clear."
"What changes now is the mentality. I feel like some of our boys, if you look at the crowd here today, so many Argentinians who have put their savings together and come for this week, next week.
"I think they've felt a bit of that pressure."
Hailing Wales coach Warren Gatland's ability to "infuse" his style into the Welsh way of playing, Cheika added: "We know we'll be well and truly underdogs" in the quarter-finals.
"As you go along you've got to get better. One thing we did do today is we scored some tries, we got a few more under our belt.
"Our defence wasn't as good as it's been, we sort of traded one for another."
- All seven games -
Pumas skipper Julian Montoya hailed his team's resilience.
"In terms of the game, we know it's knockout rugby," he said. "We like to be a fighting team, we fight for everything.
"The quality players Japan have, every mistake we did they capitalised with points. But the resilience of this team and coming back from tough moments is what made the difference here."
Montoya added that it was clear that "we want to play all seven games" through to the final.
"Of course we want to win every game," the hooker said, adding that there were "loads of things to improve".
"If we don't improve the things we did wrong today, I don't know if it's going to be enough."
Japan coach Jamie Joseph, speaking after overseeing his final Test in charge of the Brave Blossoms, said he "felt we were ready to play a big game of rugby".
"It was probably played the best we've played in the last four years, against a quality Argentina team."
But the former All Black and Japan international lamented "soft moments where we make mistakes".
"We conceded some soft tries, that's the hurting part but it will go away with time.
"In terms of winningness, to play our kind of rugby against an experienced and physical Argentina, I'm very proud of my team."
Joseph refused to be drawn on who might take over from him as Japan coach, insisting that whoever does, they must be a "guitar player" to manage the different cultures within the squad.
"I'm just the guy who gets them all together - next man up, somebody will take care of it. In really tough and difficult circumstances, they've been able to get from the 2019 World Cup to a stage where they can be proud of at this World Cup."
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