England came into the Rugby World Cup on a subdued note after losing to Fiji for the first time in August.
They now turn their attention to next Sunday's rematch in the quarter-final after another less than convincing performance against a Pacific Island side, Samoa on Saturday.
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Steve Borthwick's team needed a 73rd minute Danny Care try to win their last Pool D game.
"We have a choice with what we do with it," said Borthwick.
"We have to turn that into motivation for what we can do better and I'm sure we can.
"There were areas that were scrappy. We were put under enormous pressure and there were periods where we weren't up to standard.
"As of Monday, we'll start Test week, and the quarter-final," he added.
Fiji needed just a point against Portugal on Sunday and claimed it, although in uncovincing fashion after a last minute defeat.
During the World Cup campaign, Borthwick's side have failed to click with ball in hand.
The former Test captain, who took over from the sacked Eddie Jones in December, has experimented with a playmaking axis of George Ford at fly-half, Owen Farrell at fly-half and Marcus Smith at full-back in an attempt to put it right.
England's problems in attack have failed to convince onlookers that they improve on 2019 when they finished runners up in Japan.
Two weeks after the historic Fiji defeat, England clinically overcame Argentina in their group opener before beating Japan, Chile and Samoa, conceding just 39 points across their four World Cup games.
The wins came with Farrell, No. 8 Billy Vunipola and flanker Tom Curry, all missing games due to suspensions.
"We didn't play well and it galvanised us as a team," lock Maro Itoje said of the Fiji loss.
"It brought us tighter and we did what we did against Argentina in another set of challenging situations," he added.
Only hosts France and holders South Africa have better defensive records than England during the tournament, but Fiji will provide a test.
The Pacific Islanders include backline game-breakers such as Semi Radradra, Josua Tuisova and Waisea Nayacalevu.
"We know we have to play properly," Itoje said.
"If we're not sharp, and on it, then it's a flip of a coin and we leave it to chance," he added.
Outsiders Fiji, coached by ex-Test lock Simon Raiwalui, are poised to make the last eight mainly thanks to an impressive Australia win earlier in the competition.
"They've showed they're a top team," Itoje said.
"The lines have been blurred between Tier One and Tier Two.
"I think it disrespectful to call them Tier Two, they're probably Tier One now in terms of the quality they're producing.
"We have to put our best foot forward," he added.
