Australia batsman Steve Smith took the field on the fifth day of the first test against South Africa at Kingsmead on Tuesday, easing concerns he had suffered concussion while batting on Monday.
Smith, 37, was struck on the helmet by a bouncer from South Africa fast bowler Anrich Nortje.
Although he carried on batting, he did not field when South Africa started their second innings on Monday afternoon.
Cricket Australia said later on Monday he was undergoing assessments.
Although there was no immediate official statement on Tuesday, Cricket Australia's protocols mean he would not be able to play for a minimum of 24 hours if he was diagnosed with a concussion.
Smith practised with his teammates before play on Tuesday and took the field in his normal position at slip.
Australia were seeking to take a 1-0 lead in the three-match series, needing six wickets to wrap up the match. South Africa resumed on 102 for four after being set an improbable 421 to win.