Maurizio Sarri's decision to rest Cristiano Ronaldo backfired as Juventus was forced to settle for a 1-1 draw at promoted Lecce.
Matthijs de Ligt's handball enabled Marco Mancosu to score from the spot in the 56th minute and earn the host its first home point of the Serie A season at Stadio Via del Mare.
Paulo Dybala, the hero of Juve's midweek Champions League win over Lokomotiv Moscow, had not long earlier opened the scoring with a spot kick of his own.
But there was no late saviour for Sarri's men on this occasion, the loss of Miralem Pjanic to a muscle problem compounding a result that will force them back into second place if Inter beats Parma later on Saturday.
Juve felt aggrieved not to be awarded an early penalty for Panagiotis Tachtsidis' trip on Emre Can.
Further appeals were waved away when Danilo went down under close attention from Marco Calderoni.
Gonzalo Higuain did turn home Alex Sandro's angled drive in the 15th minute, but the goal was disallowed for offside following a VAR review.
The striker then guided a low shot across the face before Lecce goalkeeper Gabriel denied Dybala amid sustained Juve pressure.
There was no stopping the Argentina international from 12 yards five minutes after the interval, referee Paolo Valeri having finally pointed to the spot after replays confirmed Jacopo Petriccione's challenge on Pjanic took place in the box.
A second spot-kick quickly followed as Calderoni's cross from the left fizzed against De Ligt's arm.
Lecce captain Mancosu made no mistake and the Bianconeri's problems soon grew greater, with Federico Bernardeschi's failure to score after rounding Gabriel preceding Pjanic's forced withdrawal.
An injury issue for Mancosu effectively left Lecce, which had used up its substitutes, to defend with 10 men for the final 15 minutes.
But Leonardo Bonucci's errant volley was the closest Juve came to capitalising, the point ultimately edging it two ahead of second-placed Inter.
What does it mean? Sarri to reconsider rotation
Criticised in the past for failing to rotate his squad, Sarri gambled on doing so against an opponent expected to offer little resistance.
In future, if tempted to rest key players, he will surely at least keep them in the matchday squad, which Ronaldo did not make.
Gabriel sets sturdy base for stoic Lecce defence
Lecce boss Fabio Liverani can be mightily proud of the way his defenders put their bodies on the line to make repeated blocks.
Their sacrifices might have counted for little if not for Gabriel's first-half heroics, with the goalkeeper deserving of praise for his superb save from Dybala and for keeping calm under pressure thereafter.
Bernardeschi to blame for wasteful finishing
Ronaldo's absence afforded Italy international Bernardeschi a place in the starting XI but he failed to grasp the opportunity.
The attacking midfielder's heavy touch scuppered a promising first-half opening but it was his inability to shoot the right side of the post with the goal at his mercy in the second half that will linger in the mind.
Both sides are in action again on Wednesday. Juve looks to bounce back when it hosts Genoa, while Lecce visits Sampdoria.
- BCCI extends contract of India head coach Rahul Dravid and support staff
- Vijay Hazare Trophy 2023 LIVE Score, Round 4: Natarajan picks four wickets for TN vs Baroda; Mumbai beats Pondicherry
- NBA roundup: Kings stun Warriors, advance in tournament
- India to tour Sri Lanka in July-August, 2024 for six-match white-ball series
- IND vs AUS, 3rd T20I: With so much dew even 14 runs per over would have been chased, says Gaikwad defending Prasidh and co.