Steve Smith retired hurt on 80 after being hit on the head by a Jofra Archer bouncer during the second Test, before resuming his innings and going on to make 92

Australia batsman Steve Smith has been ruled out of the third Ashes Test after suffering a concussion.

Smith, 30, was hit in the neck by a 92mph bouncer from Jofra Archer on day four of the second Test, but passed an initial concussion test and returned to continue his innings.

Coach Justin Langer confirmed his absence after Smith sat out Australia's training session on Tuesday.

Smith has scored 142, 144 and 92 in his three innings so far in the series.

It has not been confirmed who will replace Smith in the Australia team for the third Test at Headingley, which starts on Thursday.

Former captain Smith was replaced by Marnus Labuschagne in the second Test at Lord's, with Labuschagne becoming Test cricket's first concussion substitute.

He made 59 as Australia survived a tense final evening to claim a draw and preserve their 1-0 series lead with three matches to play.

Brain injury charity Headway said it was "incredibly dangerous" for Smith to resume his innings.

"You need to take an 'if in doubt' approach," said Headway deputy chief executive Luke Griggs.

"With concussion, the vision can be blurred and the brain can be slow at processing information. That leads to delayed reaction times and is just incredibly dangerous."

"At the end of the day it was really a no-brainer, he felt a bit better yesterday but he is not going to have time enough to tick off everything he needs to do to be ready to play," Langer explained on Tuesday.

Ashes 2019: Steve Smith's absence from third Test is massive blow for Australia

Advantage England? - analysis

BBC cricket correspondent Jonathan Agnew

This is a huge advantage for England as Smith was holding Australia's batting together, but if he is not right and the medics say he is not right then he simply should not be playing.

I remember former South Africa captain Graeme Smith hit his head during fielding practice and he had concussion but went out and batted. He got 50-odd and he described almost seeing 'three balls' and the whole place 'moving around' behind.

It's sad for Smith and a reminder of the damage a cricket ball can do but it is also a good thing these protocols are in place and keeping people safe.

This is what happens in sport. Smith had batted for four hours and it was just a minor misjudgement. It's a scary reminder of what top-level sport and cricket can do.

But you can't ban bouncers. It's like telling Usain Bolt not to run as fast as he can.

England will discuss top seven - Bayliss

Meanwhile, England head coach Trevor Bayliss says the hosts may consider shuffling their top seven for the third Test in Leeds.

Jason Roy has opened the batting in the first two Tests of the series but has struggled against the red ball, although Bayliss said his form at the top of the order is not a concern.

"We think we've got the best seven batters available to us at the moment in England," he said.

"Whether we can change it round and make that (order) any better, I'm not sure, but we'll certainly have a discussion about it.

On Roy, Bayliss said: "Personally, I think he probably is suited to the middle order but we've selected him at the top of the order because of his form in the one-dayers and experience in the one-day team, playing international cricket.

"At the start of his one-day career, he missed out a few times as well and it took him a little while to get the hang of it.

"So the possibility of him playing again at the top of the order doesn't really concern us. We know what he can do when he does play well."