Osasuna defeated La Liga leaders Barcelona’s with an emphatic 4-2 victory on Saturday.
The Catalans won all seven of their opening fixtures but Hansi Flick’s rotated side came badly undone in Pamplona as Ante Budimir scored a brace either side of Bryan Zaragoza’s strike.
Pau Victor had given Barca a lifeline to pull them back into the game before Budimir bagged his second from the penalty spot.
Abel Bretones added a sensational fourth from the edge of the box, before Lamine Yamal pulled one back with a fine effort of his own.
Victory would have matched Barcelona’s best ever start to a league campaign with eight consecutive wins, but they were not able to build on their four-point lead on second-place Real Madrid.
The Spanish champions visit Atletico Madrid, third, in a derby clash on Sunday.