Argentina coach Mario Ledesma fears his side will be punished by England if they fail to improve on Saturday's performance against Tonga.
Julian Montoya's first-half hat-trick helped the Pumas triumph 28-12 in Higashiosaka, providing a morale-boosting bonus-point win after their opening Pool C loss to France.
It is England up next for Ledesma's men and he urged his team to up their game for the clash with Eddie Jones' side in Tokyo.
"Even if this was our best performance, it's not enough to play against England," Ledesma said.
"Losing the ball and missing tackles will make it very difficult.
"They have come here to win the World Cup – Eddie has been telling you that for the last four years."
Tonga were left to rue a slow start that saw them fall 28-0 down within half an hour.
Hopes of a comeback were stifled when winger David Halaifonua was denied a try by Tomas Lavanini's intervention, which Tonga coach Toutai Kefu felt was illegal.
"I thought it was a try – I thought it was a shoulder charge," he said.
"I looked at the front view – he did wrap his right arm and I think that's why they probably got called off, but I thought there were a couple of 50-50s we didn't get. It was critical for us.
"I'm used to it after four years of Tier 2. You move on. But had we got that, we would have come out with a lot more belief. It was not to be."