Zinedine Zidane made four substitutions at half-time on Saturday but could not spark Real Madrid into life as his team slipped to a 1-0 defeat by newly-promoted Cadiz in La Liga.
Sergio Ramos was the only enforced change at the Alfredo di Stefano Stadium as Madrid’s captain spent the second half in the stands with ice strapped around his left knee.
Madrid said the injury was not serious but it puts in doubt Ramos’ involvement in their first Champions League game against Shakhtar Donetsk on Wednesday, as well as the Clasico three days later.
If Barcelona’s players were watching, they might well feel this Madrid are there for the taking when they meet at Camp Nou next weekend.
A prolonged absence for Ramos would cap a deflating night for the reignings Spanish champions, whose dreary display certainly hands an early boost to their title rivals.
Atletico Madrid had earlier beaten Celta Vigo 2-0, with Luis Suarez opening the scoring at Balaidos, while Barca were about to face Getafe.
This is Cadiz’s first season in the top flight in 14 years and their first victory over Real Madrid in 29, yet they could have won by more.
Their reward is second place in the table, denied a place at the top by their opponents only on goal difference.
Isco, Luka Modric and Lucas Vazquez were the other three players to be hauled off by Zidane, who was reacting to an abject display from his side in the first half.
Eder Militao, Casemiro, Fede Valverde and Marco Asensio came on while a surprised-looking Toni Kroos also departed in the second period, replaced by Luka Jovic.
But Madrid’s performance hardly improved and by the end they had managed just two shots on target.
Cadiz could have been three up in the first quarter of an hour as Ramos prevented Alvaro Negredo’s finish from rolling in before Negredo created the opener.
His cushioned header put through Anthony Lozano, who skipped beyond Madrid’s sleepy defence and poked over the onrushing Thibaut Courtois.
Madrid might have equalised in the second half as Vinicius Junior headed wide of an open goal and Karim Benzema rattled the crossbar with a long-range shot.
But Cadiz were not overly troubled.
Earlier, Suarez partnered Diego Costa for the first time and scored as Atletico Madrid beat struggling Celta Vigo 2-0.
But the Suarez-Costa combination came to an early end as Costa was forced off injured in the second half.