Australia opener Matt Renshaw's withdrawal from the SCG Test has reignited cricket's concussion substitute debate, with team doctor Peter Brukner saying there is pressure on administrators to act.
Renshaw is spending Friday in a darkened hotel room and will play no further part in Australia's third Test against Pakistan, having been diagnosed with concussion after two hits to the helmet.
The 20-year-old was hit on the grille when batting on day one of the third Test then struck on the top of the helmet while fielding at short leg on day three.
On both occasions, Brukner assessed Renshaw and gave him the OK to stay on the field.
However, Renshaw left the field during Thursday's final session complaining of a headache and his condition worsened to a point on Friday morning that Brukner deemed he had concussion.
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It will leave Australia one batsmen short in their second innings, which would be a major disadvantage if the match wasn't so lopsided.
Brukner has played a leading role in reforming Cricket Australia's approach to concussion, including istigating the advent of a substitute at domestic one-day and Twenty20 level this summer.
But the International Cricket Council (ICC) blocked CA's request to change the laws governing first-class cricket and there no prospect of the rule being rolled out in international fixtures.
"The more experience we have with this, the more common it is, the more pressure there will be on the ICC to do a concussion sub," Brukner said.
"We've introduced it in non first-class cricket in Australia and it was successful. It certainly needs to be looked at very seriously by the ICC.
"In this case the coach and captain have been absolutely supportive.
"(But) the concern is without a concussion sub there's a lot of pressure on the player and the coach to allow the player to continue.
"They don't want to let the team down, don't want to be a player short.
"It would be helpful in that regard if we had a sub, it would make it easier to pull players out with a concussion."
Renshaw will be assessed over coming days, with no clear date on his return.
"Recovery from a concussion is very variable. It can take hours, it can take days," Brukner said.
Renshaw scored his maiden ton after recovering from Tuesday's bouncer blow on 91 and more than doubling his score in a knock of 184.
"We'll never know if he'd only had that one hit yesterday, whether he'd have the same symptoms or not," Brukner said.
"There is sometimes a suggestion in the research that cumulative blows may be a factor, but it's very hard to say. He was certainly hit hard enough yesterday to have had a concussion just as a one off."
Brukner was confident he made the right call to allow Renshaw to stay on the field on both occasions.
"We were joking. He answered all the questions perfectly well but then over the next 15 minutes or so he developed an increasing headache with a little bit of dizziness and felt unwell," Brukner said.
