Matt Renshaw will play no further part in Australia's third Test against Pakistan after being withdrawn due to concussion.
On Thursday, for the second time in the match at the SCG, the 20-year-old was struck on the head and left the field complaining of a headache.
Renshaw was under the helmet at short leg when a shot from Sarfraz Ahmed hit him and, although he initially tried to carry on, he was unable to continue.
Two days earlier the opening batsman had been struck on the grille of his helmet by a Mohammad Amir bouncer while batting in Australia's first innings.
Ahead of the start of play on day four, Cricket Australia confirmed Renshaw would not feature again for Steve Smith's side in the match.
JUST IN: Matthew Renshaw has been withdrawn from the third #AUSvPAK Test with concussion-- cricket.com.au (@CricketAus) January 5, 2017
"Matthew Renshaw was struck on the helmet fielding close-in on Thursday afternoon and came off complaining of a headache," said Bupa Support Team doctor Peter Brukner.
"He rested in the dressing room and then, when we returned to the hotel, we performed concussion tests and his cognitive, balance, co-ordination and reaction times were all within normal limits.
"However, on Friday morning he was still symptomatic and so we have taken the decision to withdraw him from the match as he is suffering from concussion.
"We will continue to monitor him over the coming days and work with him to produce a gradual return to play."
There was better news regarding Matthew Wade, though, the wicketkeeper cleared to play after he also failed to finish the day's play on Thursday due to illness.
Australia hold a commanding position in the Test with Pakistan resuming on 271-8 in reply to the hosts' first-innings total of 538-8 declared.