Chelsea coach Maurizio Sarri ruled out talk of his side challenging for the Premier League title despite moving top of the table by edging Arsenal 3-2 in a thrilling London derby on Saturday.
Sarri's side have maximum points from their opening two games under the Italian, but made life difficult for themselves after racing into a 2-0 lead inside 20 minutes through Pedro Rodriguez and Alvaro Morata.
Arsenal were level by half-time as Henrikh Mkhitaryan and Alex Iwobi netted.
Yet the Gunners were left to rue wasting a host of other glorious chances before Eden Hazard came off the bench to swing an enthralling encounter Chelsea's way by providing the cross for Marco Alonso's winner.
And Sarri believes those defensive deficiencies showed Chelsea are far from the finished product capable of challenging favourites Manchester City and Liverpool for the title.
"Not in this moment," said Sarri, who bemoaned a "horrible" final 15 minutes of the first-half that saw Chelsea throw away their advantage.
"I think we have to work, improve in the basics and I'm not talking about only the defenders.
"The defensive phase is about the team. If we press very high we are able to do well, but in the other moments when we are not able to press in the other half we are in trouble."
Sarri believes Hazard isn't yet ready for 90 minutes after his exertions with Belgium at the World Cup, but acknowledged his side will be a different prospect once his star man is up to speed.
And Hazard warned he isn't keen on starting a third straight game on the bench next weekend at Newcastle on the bench.
"It is better to be on the pitch than watching on the bench," said Hazard.
In contrast to Sarri's super start, new Arsenal boss Unai Emery is still waiting for his first Premier League point.
But after being outclassed by City on the opening weekend of the season, there were far more for positives for the Spaniard.
"I think we need to give the players calm and continue working," said Emery.
"The reaction after the 2-0 is very good. The 2-2 (at half-time) is soft for us because we had more chances to score."
- Jorginho key -
Chelsea beat City to the signing of Jorginho to reunite the Italian international with Sarri after three seasons together at Napoli and he is already becoming key to Sarri's change of system at Stamford Bridge.
A sumptuous Jorginho pass rewarded a positive opening by the hosts as he picked out Alonso and his cross was turned into the bottom corner by Pedro.
Seconds earlier Mesut Ozil had flashed a great chance wide and Arsenal's profligacy was punished again when Pierre-Emerick Aubameyang skied over with the goal at his mercy with the chance to level.
Morata raced onto a long ball over the top and turned inside Shkodran Mustafi before firing home his first goal of the season.
- Arsenal fightback falls short -
Mkhitaryan followed Aubameyang's example by somehow also blazing over an almost identical chance from close range.
The Armenian made amends to spark Arsenal's fightback eight minutes before the break, though, with a fiercely struck low shot that had too much power for the world's most expensive goalkeeper, Kepa Arrizabalaga.
If Kepa could have been questioned for the first goal he has conceded in English football after an 80 million euro move from Athletic Bilbao, he was helpless as Arsenal equalised four minutes later when Iwobi smashed home Mkhitaryan's cross.
Both sides tightened up after the break, but Sarri had the trump card when he introduced Hazard in the final quarter for a match-winning cameo.
Chelsea's number 10 eased past Hector Bellerin before providing a low cross for Alonso to sweep home 10 minutes from time.