Smith subbed out, in doubt for Headingley Test

Steve Smith is in doubt for next week's third Ashes Test after being ruled out with concussion and replaced by Marnus Labuschange for the final day of the second Test at Lord's.

Smith suffered a delayed concussion response to the blow on the back of the neck by a rapid Jofra Archer bouncer after lunch on Saturday.

The 30-year-old passed a series of concussion tests after the incident and was cleared to resume his innings, but woke up on Sunday morning with a "bit of a headache and a feeling of grogginess".

Smith was re-tested for concussion and his condition was found to have deteriorated, which is in line with the symptoms Smith reported.   

Match referee Ranjan Madugalle approved Australia's application for a substitute under recently-introduced concussion rules, meaning Labuschagne can bat and bowl in the ongoing Test.

It's the first time a concussion sub has ever come into a Test match.

Smith will undergo a precautionary scan on his neck on Sunday, but is now in serious doubt for the third Test at Headingley, which starts on Thursday.

The ICC's playing conditions for the new World Test Championship were recently tweaked to allow players who suffer concussions during a match to be replaced in their team’s XI.

The regulations give the power to match referees to approve whether a nominated substitute is a 'like-for-like' replacement for the concussed player.

Under the terms of Cricket Australia's concussion protocol, team doctor Richard Saw will have the final say in determining whether Smith can return to play.

Per CA's concussion policy, Smith must not play or train until clearance has been provided by the doctor and he'll be prevented from any cricket activity for at least 24 hours after the diagnosis.

After the initial 24 hours, Smith may gradually return to physical activity if he gets the doctor's clearance.

CA's concussion protocol firmly states the decision to clear a concussed player must not be influenced by any coach, administrator, support staff, or the player themselves.

Where a delayed concussion has been diagnosed, as is the case with Smith, he must pass two concussion Tests – the SCAT5 (Sport Concussion Assessment Tool) and CogSport tests - before being cleared to train and play.

The non-computerised SCAT5 test requires Smith to answer a series of questions and fill out forms, while the computerised CogSport test compares a baseline assessment taken in the off-season to the test at time of injury.

Smith passed both those tests in the team dressing room at Lord's after retiring hurt following the blow to his neck, and was cleared to resume his innings before eventually being dismissed for 92.

He then faced fresh tests at Lord's on the morning of the fifth day when the concussion was diagnosed.

2019 Qantas Ashes Tour of England

Australia squad: Tim Paine (c), Cameron Bancroft, Pat Cummins, Marcus Harris, Josh Hazlewood, Travis Head, Usman Khawaja, Marnus Labuschagne, Nathan Lyon, Mitchell Marsh, Michael Neser, James Pattinson, Peter Siddle, Steve Smith, Mitchell Starc, Matthew Wade, David Warner.

England squad: Joe Root (c), Jofra Archer, Jonny Bairstow, Stuart Broad, Rory Burns, Jos Buttler, Sam Curran, Joe Denly, Jack Leach, Jason Roy, Ben Stokes (vc), Chris Woakes.

First Test: Australia beat England by 251 runs at Edgbaston

Second Test: August 14-18,Lord's

Third Test: August 22-26, Headingley

Tour match: Australians v Derbyshire, August 29-31

Fourth Test: September 4-8, Old Trafford

Fifth Test: September 12-16, The Oval