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