Action Images via Reuters/John Sibley
Billed as the glamour tie of the second round of fixtures, this weekend's London derby certainly lived up to its potential.
While goals from Alex Iwobi and Henrikh Mkhitaryan may have cancelled out Pedro and Alvaro Morata's early strikes, new Arsenal boss Unai Emery will rue a string of missed golden opportunities: both Mkhitaryan and record signing Pierre-Emerick Aubameyang fired over from close range.
A game that very few would have been able to predict, Marcos Alonso carried on his impressive attacking start to the season when, with 10 minutes to go, he finished from Eden Hazard's low cross.
While Sarri has now picked up two wins on the bounce to start his tenure in West London, Emery's Gunners side have now slumped to two defeats and have plenty of questions over a number of their biggest stars.
Two sides who could very easily meet in the Europa League final later in the year, here are five things we learned at Stamford Bridge this weekend: