Arran Brindle and Lydia Greenway are sure England's women will take nothing for granted until the Ashes have been retained.
England moved into an 8-0 lead over the Australians with victory in the first one-day international in Melbourne, Brindle and Greenway putting on an unbroken stand of 142 to see the tourists home by seven wickets.
Australia now need to win the remaining two 50-over games and two Twenty20 matches to snatch the urn back from England, but Sunday's match-winners say there is absolutely no complacency in the camp.
"It was a fantastic win," Brindle told ecb.co.uk. "We set out to put a mark on the table for the one-day series and we obviously managed to do that today.
"We take one game at a time. We've won today and put a good marker down that we will chase most things.
"I don't think you would underestimate the Australians at any point. They obviously want to come back, win every game and win the Ashes.
"Until we get those points on the board to secure the Ashes... but, even then, we do not want to take our foot of the gas either.
"We have come out here to play some good cricket and that means winning as many games as possible."
Greenway added: "It is really pleasing that we got the win today but, in general, we're not going to underestimate the Australian team.
"We have still got a job to do and we'll be refocussing again over the next couple of days and looking forward to Thursday."
England can seal the Ashes on Thursday when the second one-day international takes place at the Melbourne Cricket Ground - the series finale is in Hobart next Sunday.