Despite extending their unbeaten Premier League run at Stamford Bridge against Everton to 28 games, Chelsea were held to a disappointing 2-2 draw by the Merseyside outfit.
A run of three victories in a row had eased the pressure on Chelsea manager Graham Potter prior to kick-off, and the Blues started the game full of confidence.
Mateo Kovacic and Kai Havertz had the best of the early chances, but neither tested Jordan Pickford, and that was ultimately the story of the first half.
Shortly after the break, Havertz was denied by a Pickford save and, within seven minutes of the restart, the 2020/21 UEFA Champions League (UCL) winners had the lead.
The visitors always look threatening from set-pieces, and it was from a corner that they equalised, when Abdoulaye Doucouré got his head onto James Tarkowski’s effort at goal.
Reece James, on one of his many forays forward, was felled in the penalty area by Tarkowski, leaving referee Darren England with an easy decision to point to the spot.
In the recent UCL victory over Borussia Dortmund, Havertz needed two attempts from 12 yards to score, but on this occasion, one sufficed as the Germany international sent Pickford the wrong way.
Just as it seemed Chelsea were going to hold on to pick up all three points, substitute Ellis Simms popped with a vital goal for his side, making a fool of Kalidou Koulibaly on his way to slotting past Kepa Arrizabalaga.