Sunderland caretaker manager Billy McKinlay has quit the club to join David Moyes at West Ham United.
The Scot, who was handed the first team reins alongside Robbie Stockdale after Simon Grayson's departure, will link up with the former Black Cats boss as part of his backroom staff at the London Stadium.
McKinlay had joined Sunderland under Moyes as his chief scout, but has management experience with Fulham and Norweigan side Stabaek.
He also served as Moyes' assistant coach during his spell at Real Sociedad.
His departure is another blow to Sunderland, who are still without a manager almost two weeks after Grayson was sacked.
It means Stockdale will take training this week in preparation for the Millwall game on Saturday, while Martin Bain continues his hunt for a new manager.
Moyes replaced Slaven Bilic as Hammers boss last week, and has moved quickly to get his backroom staff in place, with 48-year-old McKinlay joining him with immediate effect.
A club statement said: "Sunderland AFC can confirm that Billy McKinlay has taken up a coaching role with West Ham United.
"The club would like to thank Billy for his efforts during his time on Wearside.
"Robbie Stockdale will continue as the club’s caretaker manager when the squad returns to training on Monday.
"A further announcement will be made in due course."