Eddie Howe quit unexpectedly Newcastle United after a 4-1 loss to Bristol City, Sky Sports News said.
Sky aired his last interview briefly.
He briefly talked about the Bruno Guimaraes signing before walking out without delay.
Former player Jay Bothroyd warned strongly the club could face risk of relegation without Howe.
Sky Sports will exclusively broadcast the national Scottish Premiership opener on Saturday.
Dundee United take on Rangers at Tannadice.
Manager Jim Goodwin clearly said he wants to make an impact there.
Dundee United coach Derek McInnes confirmed two United players are missing and several are uncertain.
Rangers look forward to Thelo Aasgaard and Cammy Devlin to be available for the match.