MELBOURNE : Australia are optimistic that David Warner will have a big Ashes and have backed him to deliver at the top of the order.Selectors had equivocated on whether the lefthander was locked in for the Ashes series against England after a difficult tour of India but head coach Andrew McDonald offered a firm endorsement on Wednesday."We're optimistic with what Dave's got left, we’ve picked him in the squad and we feel he’ll play a really big part in the Ashes and the World Test Championship," McDonald told Australian radio station SEN.Warner was included in Australia's squad for the WTC final against India and the first two Ashes tests but selectors kept their options open at the top of the batting by also calling up Marcus Harris and Matt Renshaw."He's an important part of that squad, and if he wasn’t, we would’ve had a clear checkpoint after the WTC going into the Ashes," added McDonald."That’s not the case, we’ve picked our squad for the first two Ashes tests as well, so he’s clearly in our plans and ready to go."Apart from a defiant 200 against South Africa in December, Warner has struggled for runs in recent tests, making a total of 26 in three innings in the recent tour of India before returning home injured.He had a dire series in England during the last Ashes tour, averaging 9.50, the worst ever by an opener to play 10 innings in a series, with paceman Stuart Broad taking his wicket seven times.He had a better time of it in 2015, scoring 418 runs at an average of 46.44.Warner finished the Indian Premier League for Delhi Capitals with 516 runs at an average of 36.86, down on his career average of 41.54."He's in a good head space," said McDonald."I spoke to him as recently as yesterday, and he's ready to go.