Rafa Benitez has been unable to return to Newcastle United's training ground after surgery late last week.
The Independent report that Benitez had an operation in Cheshire to remove an infection related to a hernia operation he had two years ago.
United's manager – who had had the procedure during the international break to minimise disruption to the team's preparations – had planned to take charge of training yesterday.
However, Benitez has been unable to return to the club's Benton HQ because of the "severity of the infection", according to the report.
Benitez is said to be "adamant" that he will take charge of the team for Sunday's Premier League game against Swansea City at the Liberty Stadium, though he will have to listen to medical advice.
The 57-year-old last visited the training ground on Thursday afternoon for a brief meeting meeting with managing director Lee Charnley.
Benitez was angered by Newcastle's failure to strengthen on transfer deadline day.