Arsenal's 14-match unbeaten Premier League run might have convinced manager Arsene Wenger that they had developed the resolve needed sustain a title challenge but there was little sign of that quality in Tuesday's 2-1 defeat at Everton.
Wenger said his side had struggled to deal with Everton's physical approach as the Merseysiders fought back to win 2-1 thanks to Ashley Williams' late header at Goodison Park.
It had all been going so smoothly for Arsenal when the in-form Alexis Sanchez had put them ahead with his 12th league goal of the season from a deflected free kick after 20 minutes.
But Everton upped the intensity levels and clawed their way back into the game through fullback Seamus Coleman's header just before halftime and Williams won it in the 86th minute.
"...we faced many physical challenges and that disturbed our game but we were a bit unlucky to lose as well," Wenger told BT Sport television in a familiar refrain for Arsenal fans who have become used to seeing successive title challenges fall away.
"They (Everton) were a bit scared at first but they got their confidence. We did fight, I cannot fault that... Maybe we made it easy for them when they became more physical."
The defeat was Arsenal's first in the league since their opening day loss at home to Liverpool, but it left them three points adrift of pacesetters Chelsea, whose game in hand is against bottom club Sunderland on Wednesday.
When Arsenal visit Manchester City on Sunday, they could conceivably be nine points behind Antonio Conte's league leaders, who travel to Crystal Palace the day before.
Having drawn Bayern Munich in the Champions League's round of 16, Arsenal, whose last Premier League title was back in 2004, will need to be careful to ensure another season that has begun with such promise does not peter out.
That is likely to depend on whether the team's previously free-scoring forwards can maintain their early season form.
Having scored 12 goals in their previous three games in all competitions, Arsenal, the Premier League's joint top scorers with 37, were largely blunted by a resolute Everton.
The London side's glittering attacking talents Mesut Ozil and Sanchez were starved of service and looked short on energy in a laboured display.
Wenger, however, felt that was down to how resolute Everton were defensively.
"They defended well even when we controlled the game," Wenger added. "We created chances but not too many were clear-cut. We battled hard. We put everything in and the players are very disappointed."
(Reporting by Toby Davis; Editing by Ken Ferris)