Australia batsman Steve Smith has been ruled out of the remainder of the second Ashes Test with a concussion.
Cricket Australia says Smith, who was hit on the side of the neck by a vicious delivery from England paceman Jofra Archer on Saturday, woke with a "bit of a headache and a feeling of grogginess."
Smith retired hurt before returning to the middle 40 minutes later after passing concussion tests. Cricket Australia said Smith suffered a delayed concussion.
Marnus Labuschagne has been approved as Smith's replacement after Australia applied for a concussion substitute, which was introduced to international cricket on Aug. 1.
Smith is in doubt for the third Ashes Test starting in Leeds on Thursday.
Earlier, Smith retired hurt for 40 minutes in the second Ashes Test at Lord's after being struck on an unprotected part of his neck by Jofra Archer during a hostile spell of bowling by the England paceman.
A rising delivery by Archer knocked Smith, who was wearing a helmet, to the ground and England's players were quick to show their concern. After receiving medical treatment, Smith was back on his feet but left the field for assessment, to applause by spectators at the home of cricket.
He returned to resume his innings on 80, and progressed to 92 before he was trapped lbw by Chris Woakes. Australia were 234-8 in reply to England's first-innings total of 258.
