Barcelona were brought back to earth after their remarkable Champions League victory over Paris St Germain as they slumped to a 2-1 defeat at lowly Deportivo La Coruna in La Liga on Sunday.
Joselu, on loan from Premier League side Stoke, opened the scoring for the hosts with just five minutes remaining of the first half at the Riazor.
Luis Suarez drew the defending champions level moments after the interval with his 21st league strike of the campaign, but Alex Bergantinos headed home Depor's winner with 17 minutes to go.
Barcelona's defeat was only their third in La Liga this season and brought to an end a six-match winning streak in the division, a run which had seen them replace Real Madrid at the top of the table.
Luis Enrique's side headed to relegation-threatened Deportivo just four days after their miraculous victory against PSG, when they overturned a 4-0 first-leg deficit with a 6-1 win at the Nou Camp to seal their place in the record books and in the quarter-finals of the Champions League.
Barcelona were without Neymar at the Riazor, sidelined with an adductor issue he sustained while starring in Wednesday's win, and Rafinha was missing with gastroenteritis.
Depor faced the league leaders unbeaten in their last three matches and, despite sitting just one place above the drop zone, enjoyed the better of the chances on what could prove to be a pivotal match in the race for the title.
The breakthrough came for Depor after 40 minutes. Barca defender Javier Mascherano failed to deal with a corner and while Marc-Andre ter Stegen managed to get his fingertips to the ball, Joselu rifled home from two yards out.
Barca headed into the interval one goal down, but responded only 90 seconds after the restart. The Depor defence failed to deal with Denis Suarez's cross from the right-hand side and his namesake Luis was on hand to net the equaliser.
It should have marked as the incentive for Enrique's side to go on to win the game, but acted only as a tool of inspiration for the hosts.
Indeed it was Ter Stegen in the visiting goal who was called into action on more occasions than Depor counterpart German Lux, and with 17 minutes left an unmarked Bergantinos headed the winner from a corner.
The shell-shocked visitors went in search for an equaliser. Luis Suarez looked set to draw his side level with just 10 minutes left but his close-range effort was expertly saved by Lux. Lionel Messi then blazed over in stoppage time from a free-kick as Depor held on to move up to 15th.