London Irish battled to claim a draw at Bristol Bears despite seeing Ollie Hoskins sent off on the stroke of half-time.
Exeter Chiefs were in control at half-time, but Bristol Bears scored 20 points without reply in the second half to snatch a stunning win.
Saracens were on the brink of a second defeat in three Premiership games but they battled back to defeat London Irish.
Northampton Saints and Gloucester followed up narrow away wins on the opening weekend by easing to home successes in the Premiership.
Wasps fell just short in their comeback bid as London Irish made a winning start in their return to the Premiership.
Sean O'Brien, who will join London Irish later this year, is to miss the Rugby World Cup for Ireland with a hip injury.
Adam Coleman will join Waisake Naholo, Sekope Kepu, Paddy Jackson and other new signing at London Irish in the Premiership next season.
London Irish continued their spending spree ahead of their return to the Premiership by sealing a move for Waisake Naholo.
Paddy Jackson will leave Perpignan after a single campaign in France, joining London Irish for their return to the Premiership.
London Irish have boosted their squad ahead of their return to the Premiership, signing Australia prop Sekope Kepu.