Ashes 2019: Steve Smith injury brought 'rough memories' of Phillip Hughes
Coach Justin Langer admitted Steve Smith's injury at Lord's reminded him of the tragic death of Australia batsman Phillip Hughes.
Smith was struck on the neck by England fast bowler Jofra Archer and retired hurt, before returning to make 92.
Hughes died aged 25 in November 2014, two days after being hit by a ball when batting in a domestic match.
"There's obviously some rough memories of a blow like that, there's no fun in it," Langer said.
It was a torrid afternoon for Australia's premier batsman Smith, who made two centuries in the first Test victory at Edgbaston.
The 30-year-old, batting without an arm guard, was first struck on the forearm by debutant Archer, who bowled consistently in excess of 90mph and sent down one delivery timed at 96mph.
Former Australia skipper Smith, who was stripped of the captaincy and served a 12-month ban for his role in a ball-tampering scandal during the Test series in South Africa last year, was on 80 when a short ball rose and struck him on the side of the neck. After lengthy discussions with the Australia medical team Smith was persuaded to leave the field.
"He went through the concussion protocols and seemed to be coming up OK," Langer explained. "He passed all that and he came back in the changing room and had a bit of a smile on his face, he was more worried about his arm, thankfully that's OK, he's had an X-ray on that at the hospital this afternoon.
"I'm sure he'll be very sore tomorrow, his arm and his neck but he was in good spirits.
"He passed all the testing and that's why he came back out."
'Like my sons'
Smith did not take the field when England began their second innings but Langer expects his star batsman to play a role in Sunday's final day, when the hosts will resume 104 runs ahead with six wickets intact.
"As is the protocol he'll have another test in the morning so there is no residual concussion and I suspect he will play the game out there," Langer added.
"These are like my sons so you are never going to put them in harm's way, but he was determined.
"He said 'I can't get on the honours board unless I'm out batting.' All he was worried about was that he wasn't going to be able to play his forward defence because his top hand grip was hurting.
"I asked him over and over, privately two or three times and in front of the group, the medical team cleared him and he said he was ready to go."
Smith was also not wearing the attachment to the helmet that protects the neck now favoured by most players. Langer said: "I didn't realise they weren't mandatory until today, but I think Steve wrote in his book that he doesn't feel comfortable, he has all these little idiosyncrasies everyone talks about, he doesn't like shoelaces he can see, he just doesn't feel right. I am sure it will get talked about again, I know they came in after the tragedy of Hughesy.
"He might re-think it but at the moment the players have a choice. I wouldn't be surprised if they become mandatory in the future."