Eddie Howe quit suddenly Newcastle United after a 4-1 loss to Bristol City, Sky Sports News said.
Sky aired his last interview publicly.
He briefly talked about the Bruno Guimaraes signing before walking out without delay.
Former player Jay Bothroyd warned sternly the club could face danger of relegation without Howe.
Sky Sports will exclusively broadcast the premier Scottish Premiership opener on Saturday.
Dundee United welcome Rangers at Tannadice.
Manager Jim Goodwin confidently said he wants to plant a flag there.
Dundee United coach Derek McInnes announced two United players are absent and several are questionable.
Rangers anticipate Thelo Aasgaard and Cammy Devlin to be available for the match.