Sheffield United battled back from two goals down to snatch a point after Kurt Zouma’s late own goal at Stamford Bridge.
The hosts were 2-0 up by half-time after striker Tammy Abraham struck twice for his third and fourth goals of the season.
But the Blades pulled one back in the first minute of the second half when Callum Robinson, who had missed from close range in the first half, scored his first since joining the club in the summer.
And they pulled level after 89 minutes when Robinson’s cross towards substitute Lys Mousset was diverted into his own net by the unlucky Zouma to leave Frank Lampard still searching for a first home win since he became Chelsea manager.
Chelsea struggled to threaten after United keeper Dean Henderson made a brilliant save in the second half to deny Abraham a hat-trick.
The result puts the visitors, who finished second in the Championship last season, into eighth in the Premier League table, one place above Chelsea.
Blues good start undone
After a loss and a draw in their first two league games, Chelsea’s 3-2 win at Norwich last week had finally given Lampard the result that he felt his side had deserved based on their performances from the start of the season.
And when Chelsea were 2-0 up by half-time, that upwards trend looked to be continuing – but a flat second-half display undermined the good work of earlier, especially by Abraham.
The 21-year-old was quick to react when a mistake by Henderson allowed him a sharp chance from six yards for his first.
And he was equally alert when a mistake by Jack O’Connell and John Egan conspired to give him the opportunity to fire the ball home from the edge of the box off Henderson’s hand and just inside the post.
But the Blades keeper’s excellence when dropping low to turn Abraham’s header away after the break proved to be the turning point, with Chelsea looking tired and short of ideas in the face of their spirited opponents.
The home crowd became increasingly edgy, which seemed to transfer to their team and it came as little surprise when Sheffield United equalised.
Lampard’s starting 11 was the youngest Chelsea have named in the Premier League era with an average age of 24 years and 158 days, and they will have to learn how to close out this kind of encounter if they are to settle into the upper reaches of the table.
Blades take their chances when it matters
Blades manager Chris Wilder had not been impressed by his side’s efforts in their 2-1 defeat by Leicester in their previous league outing, saying he “didn’t see why they should get applause” from the Bramall Lane crowd.
Compare and contrast with this week, when Wilder and his players celebrated this hard-won point on the pitch in front of their fans after the final whistle.
The half-time scoreline was not a fair reflection on United, who had looked threatening in their rare attacks before the break.
Chris Basham miscued a shot a long way wide after a neat United move, and Robinson missed with a low header when free inside the six-yard area.
But the former Preston striker’s first goal for the Blades changed the momentum of the game at just the right time, and helped deflate the home side and their supporters.
A lack of Premier League experience compared to Chelsea counted for nothing, and Wilder’s side showed the value of taking chances when they come along by scoring with their only on-target efforts of the match.
Chelsea visit Molineux to take on Wolves when the Premier League returns after the international break, kicking off at 15:00 BST on Saturday 14 September. The Blades host Southampton at Bramall Lane on the same date with the same start time.
More to follow