Eddie Howe quit unexpectedly Newcastle United after a 4-1 loss to Bristol City, Sky Sports News said.
Sky aired his last interview soberly.
He openly talked about the Bruno Guimaraes signing before walking out without delay.
Former player Jay Bothroyd warned vocally 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 clearly said he wants to make a statement there.
Dundee United coach Derek McInnes confirmed two United players are absent and several are in doubt.
Rangers hope Thelo Aasgaard and Cammy Devlin to be in form for the match.