(CNN) -- Holders Barcelona must overturn a one-goal deficit in the second leg of the Copa Del Rey last-16 clash with Sevilla after a shock 2-1 loss in the home tie on Tuesday night.
Having dropped their first league points at the Nou Camp this season on Saturday, Pep Guardiola's players -- who won six trophies in 2009 -- again stumbled in front of their own fans.
Sevilla also faltered in La Liga at the weekend, losing 2-1 at Atletico Madrid, but bounced back against a much-changed Barca line-up featuring the return of world player of the year Lionel Messi.
The Argentine hit the crossbar midway through the first half, but it was the visitors who took the lead after an hour through midfielder Diego Capel.
Capel had a first-half effort ruled out for offside, but was on hand to pounce from close range when Diego Perotti's cross fell to him from Renato's clever flick.
Barca through they had leveled through a deflected effort by Bojan Krkic with 20 minutes left, but it was disallowed due to an earlier foul by half-time substitute Zlatan Ibrahimovic.
But the big Swede, who replaced Pedro at the break, made amends three minutes later when he rounded goalkeeper Andres Palop to score from a tight angle after being set free by Rafael Marquez's superb long ball.
However, the lead was short-lived as defender Dymytro Chygrynskiy was ruled to have fouled Capel from behind, allowing substitute striker Alvaro Negredo to fire the winner from the penalty spot.
Messi had a chance to level the scores late on and Dani Alves had another goal disallowed for Barca, again for offside, but Sevilla survived to take a vital lead to their Ramon Sanchez Pizjuan next week.