The Wallabies slumped to their 10th defeat in 13 tests with a 9-6 loss to Wales over the weekend, sparking a fierce reaction in Australia where rugby pundits called for Cheika's sacking a year out from the World Cup in Japan.
While there are fresh legs in the squad, including uncapped 18-year-old fullback Jordan Petaia, Australia should aim to field a strong side against the Italians in Padova, said Toomua.
"I think we've got to win, don't we?" Toomua told reporters.
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"We've got to give respect to Italy as a team who we know can upset a lot of teams. We struggled against them a few years ago back in Australia.
"So I think going out with wholesale changes wouldn't be the smartest tactic."
Australia have never lost to Italy in 17 matches but suffered a huge scare in their last meeting in Brisbane last year before overhauling the Azzurri 40-27.
Toomua said he expected some changes to the Wallabies side that Wales coach Warren Gatland described as surprisingly easy to defend against.
"We've lost a few on the trot now and ... there might be some selections that are enforced because of form rather than just giving guys a go," added Toomua.
"It will be imperative that we win the game and we win well, to get some momentum going into England.
"Cheika might have a bigger picture view in terms of a few guys here and there but I think after, particularly what happened on the weekend, we've got to get a win."
After Italy, the Wallabies finish their 2018 season against Eddie Jones's England at Twickenham next week.
(Reporting by Ian Ransom in Melbourne; Editing by Peter Rutherford)
