In the second-half, Chelsea looked more solid, and they would eventually bag the victor, with Alonso firing home from an Eden Hazard pass to secure all three points in a thrilling derby clash.
"We did very well for 75 minutes of the 90, but inside there were 15 minutes [that were] frightful", he said.
Sarri will no doubt work on Chelsea's defensive deficiencies in training this week and he also took the opportunity to announce another, more personal attempt at improvement.
Maurizio Sarri said Chelsea must improve the "quantity" rather than the quality of their best football if they are to emulate the level reached by his Napoli team. And the latest measures seem to have had an immediate impact along with Sarri's tactical inputs with Chelsea off to a blistering start in the Premier League.
'We're improving as a team altogether and the same applies to everyone - you have to show the manager that you're good enough to play.
"In the first 25 minutes we did really very well". "It is better to be on the pitch than watching on the bench", said Hazard.
But after being outclassed by City on the opening weekend of the season, there were far more for positives for the Spaniard.
"You know what I said after the World Cup", he told RMC Sport. This is always the way, but it is clear that defensively we suffered three goals but also we had chances to do more goals.
Abysmal defending from Arsenal saw Chelsea rush into a 2-0 lead thanks to goals from Pedro and Alvaro Morata.
Mkhitaryan followed Aubameyang's example by somehow also blazing over an nearly identical chance from close range.
Arsenal would score on 37 minutes, with Henrikh Mkhitaryan, who himself had missed another great chance, arrowed a left-footed shot past new goalkeeper Kepa Arrizabalaga.
Alex Iwobi made it 2-2 four minutes later as Arsenal exploited Chelsea's vulnerability on the flanks.
In tribute to Vajpayee, PM Modi walks the extra mile
Caretaker Information Minister Syed Ali Zafar attended the funeral of former Indian premier Atal Bihari Vajpayee on Friday. He further said that by creating peace between the two countries, "we can truly recognise the service of Vajpayee ".