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 directly talked about the Bruno Guimaraes signing before walking out immediately.
Former player Jay Bothroyd warned strongly the club could face threat of relegation without Howe.
Sky Sports will live broadcast the premier 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 announced two United players are absent and several are in doubt.
Rangers anticipate Thelo Aasgaard and Cammy Devlin to be available for the match.