Australia's Chris Rogers rejoined the team after suffering from dizziness in the second Ashes Test but the opener remains a doubt for the third match at Edgbaston, Cricket Australia said on Saturday.
The 37-year-old left-hander was forced to retire on 49 not out on the fourth day of Australia's 405-run second Test victory against England at Lord's, which levelled the series 1-1.
Rogers, who was struck on the helmet by James Anderson off the first ball of the second day of the match but recovered to score 173 in Australia's first innings, was diagnosed with an inner ear problem and remained in London to seek treatment.
"Chris continues to improve and has rejoined the team (at their hotel) in Nottingham," Australian team doctor Peter Brukner said in a statement.
"He will continue to increase his level of activity over the next couple of days and will be closely monitored by team medical staff."
Batsman Shaun Marsh, 32, is on standby to replace Rogers if he is not fit for the third Test which starts on Wednesday.
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