Newcastle boss Joe Kinnear is set to miss two months of the crucial Barclays Premier League run-in after being told he needs heart by-pass surgery.
PA Sport understands the 62-year-old is expected to undergo an operation later this week after tests carried out following his admission to hospital at the weekend revealed a problem which needs to be addressed.
Assistants Chris Hughton and Colin Calderwood, the latter a recent arrival at St James' Park, will take charge of team affairs as the Magpies attempt to climb away from relegation trouble.
Kinnear complained of feeling unwell at the team hotel ahead of Saturday's 3-2 victory at West Brom, and was taken to hospital after the club's medical staff realised his blood pressure was raised.
The club later released a statement confirming initial tests had shown he was "okay" and that he would be detained for further observation.
However, after being seen by a cardiologist, Kinnear has now been told surgery is required and that he will need two months of complete rest afterwards.
That will not only come as a blow to the former Tottenham and Republic of Ireland defender, who suffered a heart attack almost 10 years ago during his spell in charge at Wimbledon, but also to his current employers.
Kinnear was drafted in by owner Mike Ashley in September last year as an emergency stand-in after Kevin Keegan's untimely departure.
Ashley turned to him after failing in a bid to persuade Terry Venables to accept the job on a temporary basis, and later appointed him until the end of the season following an encouraging start.
Kinnear's reign to date has proved eventful with run-ins with sections of the media and officialdom having accompanied difficult times on the pitch.
Ironically, he missed the club's first league win since December 21 because of his latest stay in hospital, but was kept fully informed of events at the Hawthorns by his grandson.
He had initially hoped to be back in the dug-out by the time the Magpies face Everton at St James' a week on Sunday, but that is now out of the question.
Hughton was in charge of the team on Saturday, just as he had been in the immediate aftermath of Keegan's exit, although this time he will at least have former Nottingham Forest and Northampton manager Calderwood to help him.
The 44-year-old, who lost his job at the City Ground in December, is relishing the task of playing a significant role in the club's drive for safety after enjoying his first few weeks on Tyneside.
Calderwood told the Evening Chronicle: "I'm thoroughly enjoying myself. It's been refreshing and very appetising. I have found something I have really enjoyed doing.
"Sometimes it's not just the environment you walk into, it's the people you meet. I'm glad to be here, and it's given me a lift as much as anything else."