Stand in captain Matthew Wade has bemoaned Australia's poor start to the T20 World Cup, saying the team are building into their best form.

Speaking after Australia's narrow victory over Afghanistan at Adelaide Oval, in which Wade deputised for injured captain Aaron Finch, the wicketkeeper said Australia had been chasing the tournament since the opening game.

"It's been frustrating," Wade told ABC Sport.

"I don't think we've been all that good this tournament to start with, we've been a little bit slow out of the blocks, to be honest.

"It would be nice not to have copped a flogging in that first game of the tournament and been able to keep ourselves in it with the run rate a little bit more.

"If we don't get through it's going to be frustrating, to look at that first game and know that if we'd kept it a little closer we maybe could have given ourselves a chance at the back end."

Australia were thumped by New Zealand in the tournament opener, losing by 89 runs at the SCG to put their World T20 defence on the back foot from the off.

Australia's perilous net run rate situation means that, although they currently occupy second spot in the group on seven points, level with New Zealand, an England win over Sri Lanka on Saturday night at the SCG would see Australia go out of the tournament on net run rate.

Wade said Australia would "have our Sri Lanka caps on" as they watched Saturday's final Group One match decide their fate and that Sri Lanka could pose problems for England.

"They've been in good form coming into this tournament, they won the Asia Cup and they beat some good teams there," Wade said.

"Every time we play Sri Lanka it's never a guarantee. 

Australia's seven wicket victory over Sri Lanka had looked to kick-start Australia's tournament and go some way to improving that net run rate.

But a rained out clash with England, coupled with failing to put Ireland and Afghanistan away with more aplomb from promising positions, proved costly.

"We had our opportunities against Ireland probably to get some of that [net run rate] back and just didn't take them when it was there," Wade said.

In Friday's match against Afghanistan though, Australia came far closer to a tournament-ending disaster than it should have, thanks mostly to some superb late hitting from Rashid Khan's 48 off 23 balls at the death.

"It was hard work," Wade said.

"I knew it was going to be a tight one, I've played with Rash in the IPL and have seen him do that many a time in the IPL.

"[We] never really felt safe.

"Thankfully we got the win, but it would have been nice to get a little bit of that run rate back."