England boss Eddie Jones insists his side "didn't play well" despite the record-breaking victory over Australia.
The 39-28 win was England's first in Brisbane and the most points scored in any game against the Wallabies.
Jones told BBC Sport: "We didn't play well, let's face the facts. We weren't sharp in various areas, but we will be next week.
"They didn't play well, so whichever side improves the most will win the next Test, and that's going to be us."
With his squad averaging 24 years of age, Jones believes there is plenty more to come from England in the long term.
"We're going to be a very good team, maybe we don't know how good we can be, [but] maybe there was a bit more belief about us," the Australian, who guided England to just their fourth Test victory on Australian soil.
England skipper Dylan Hartley said the players must not get carried away.
"I'm really proud for the guys that they can etch their names in history, but we need to keep our feet on the ground - our egos in check - we now need to go again next week," the hooker told BBC Sport.
"We're a grounded group, we want to win the series, [and] and all our focus and energy now can go into our second game in Melbourne," he added.
Jones also confirmed centre Luther Burrell was replaced in the first half for tactical reasons.
He must decide whether to start Owen Farrell and George Ford together in the midfield, or opt for the rugby league convert Ben Te'o at number 12.
"Ben Te'o has done a bit more training so he comes into consideration, so we will have a look at that," Jones added.
"It's all about looking forward. We will recover well then we will get stuck in. This is a chance to create real rugby history."