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 briefly talked about the Bruno Guimaraes signing before walking out right after.
Former player Jay Bothroyd warned vocally the club could face threat of relegation without Howe.
Sky Sports will exclusively broadcast the national Scottish Premiership opener on Saturday.
Dundee United face Rangers at Tannadice.
Manager Jim Goodwin firmly said he wants to make a statement there.
Dundee United coach Derek McInnes announced two United players are unavailable and several are in doubt.
Rangers anticipate Thelo Aasgaard and Cammy Devlin to be in form for the match.