Barnsley striker Iain Hume was readmitted to hospital on Monday night just over two weeks after fracturing his skull in the local derby clash against Sheffield United at Oakwell.
Hume is understood to have spent the night at Salford Royal as a precaution after complaining of feeling unwell at home in Oldham.
The 25-year-old Canada international was released from hospital seven days ago and has since been recovering at home.
A Barnsley spokesman said on Monday morning: "He went back in last night because he was feeling sick.
"He began feeling unwell after spending time at home and we hope it's a case of better safe than sorry.
"We've not heard anything else this morning to suggest otherwise."
Hume was struck in the head by Sheffield United defender Chris Morgan's elbow during Barnsley's 2-1 home defeat to the Blades on November 8.
The former Leicester forward, signed by Barnsley for £1.2million in June, suffered internal bleeding and had emergency surgery after his condition later deteriorated.
Morgan, who left hometown club Barnsley for the Blades in July 2003, received a caution from referee Andy D'Urso following the incident.
But Barnsley have submitted further video footage of the incident to the Football Association, who have confirmed they are still considering whether to take further action.
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