Marco Asensio saw his penalty saved as Nacho's own goal condemned Real Madrid to a surprise 1-0 defeat against mid-table Real Mallorca in LaLiga on Sunday.
Madrid fell behind when stand-in captain Nacho deflected Vedat Muqiri's header beyond Andriy Lunin – a late replacement for the injured Thibaut Courtois – 13 minutes in.
The champions toiled for long periods without absent striker Karim Benzema, and they missed a golden chance to level when Predrag Rajkovic saved Asensio's second-half penalty.
The result meant Los Blancos missed the chance to close the gap on LaLiga leaders Barcelona ahead of their fixture against Sevilla later on Sunday, handing the Blaugrana the chance to move eight points clear.
Fresh from three successive home wins, Mallorca wasted little time in taking the lead. Muriqi met Dani Gonzalez's inswinging cross, and his flicked header deflected off Nacho before looping over Lunin.
Madrid controlled the remainder of a scrappy first half but failed to register a single shot on target before the break, with the likes of Federico Valverde and Antonio Rudiger restricted to ambitious long-range efforts that cleared the crossbar.
The visitors were presented with a wonderful opportunity to equalise on the hour mark when a VAR review ruled Rajkovic had fouled Vinicius Junior. However, the goalkeeper atoned for his error by guessing correctly to brilliantly deny Asensio.
Carlo Ancelotti introduced the likes of Luka Modric and Toni Kroos in a bid to inspire Madrid, who had lost just once in their nine previous away games against Mallorca prior to Sunday's meeting.
Substitute Mariano Diaz volleyed narrowly over and Rudiger sent a header wide late on, but the stubborn hosts clung on to deal a huge blow to the champions' title defence.