Pep Guardiola was caught in a heated exchange with Brighton defender Jan Paul van Hecke after the final whistle of the Seagulls' 2-1 win over Manchester City.
The Premier League champions slumped to their fourth successive defeat in all competitions at the Amex on Saturday evening, courtesy of second-half goals from Joao Pedro and Matt O'Riley.
City had taken the lead during a dominant first half when Erling Haaland found the net for only the second time in six matches. But the Seagulls' stunning turnaround sees the visitors lose crucial ground in the title race to table-toppers Liverpool.