Cummins drops huge surprise about Warner's Ashes fate

David Warner is set to open in the fourth Ashes Test against England, Australia captain Pat Cummins said on Tuesday, but spinner Todd Murphy could be squeezed out to accommodate both all-rounders, Mitchell Marsh and Cameron Green.

Warner's place looked uncertain after his double failure in the third Test at Headingley where the opener managed a total of five runs and fell to Stuart Broad in both innings.

"Josh will come in for Scott Boland, and the top order will stay the same," Cummins, whose team are 2-1 ahead in the five-match series, told reporters on the eve of the match at Old Trafford.

"Davey (Warner) didn't have his best game last week at Headingley, but prior to that, he has looked really good."

"He has had three 50-run (opening) partnerships, which can be rare over in England."

Replacing an injured Green at Headingley, Marsh smashed a century and grabbed a couple of wickets to make it difficult for the selectors to drop him.

With Green having recovered from a hamstring strain, left-arm spinner Murphy may have to sit out having bowled only 9.3 overs across two innings at Headingley where England won by three wickets to stay alive in the series.

With rain forecast for the last two days of the Test, Cummins was fine with the idea of not playing a frontline spinner.

"Part of the conversation is how do two all-rounders fit in, is spin going to be important this week?" the Australia captain said.

"We've played games with one quick, we've played some games with heaps of quicks. It's all really conditions-based."

"As I said last week about Toddy, I would have loved to bowl him a bit more but there wasn't a heap of overs in the game, the ball seemed to swing and seam a little bit."

"So that's certainly something to weigh up this week."