Australia coach backs Warner to play 'significant part' in Ashes
The 36-year-old opening batsman has been a mainstay of the Australian team since making his debut against New Zealand in 2011.
But the left-hander approaches the Ashes and World Test Championship final against India at The Oval with one century in his past 32 innings and a mediocre record in England.
"We're optimistic with what Dave's got left," McDonald told SEN radio on Wednesday, addressing doubts about Warner's immediate future on the side.
"We've picked him in the squad and we feel that he's going to play a really significant part in the Ashes and the World Test Championship final, and that's why he's on the plane.
"We think he's got some good games left in him."
While Warner made Australia's 17-man squad for the first two Ashes Tests and the preceding WTC final, selectors have kept their options open beyond that.
McDonald said that Warner was in "a good head space".
"He's an important part of that squad," McDonald said.
"If he wasn't, then we would have had a clear checkpoint after the first Test match or the World Test Championship going into the Ashes, but that's not the case.
"He's clearly in our plans and he's ready to go, and we're in constant contact with him," he added.
Former vice-captain Warner missed much of this year's blockbuster tour of India with a fractured elbow, which came on the back of an extended lean spell with the bat.
Warner has previously hinted at retirement from Test cricket this year to focus on the game's shorter formats.
The WTC final starts on June 7th and the first Ashes Test is on June 16th at Edgbaston.