Barca had given Messi – who was watching from the stands – a break to nurse an ankle injury, but the six-time Ballon d'Or winner's creativity and goal threat was badly missed as the hosts dropped points for the eighth time in 15 LaLiga games this season.
Martin Braithwaite was duly punished for an early penalty miss – a LaLiga-high third of the campaign for the Catalan giants – when Kike Garcia took full advantage of a Ronald Araujo error in the 57th minute.
2014/15 ❌— LaLiga English (@LaLigaEN) December 29, 2020
🔵🔴 @SDEibarEN take points at the Camp Nou for the first time in #LaLigaHistory!#KickOut2020 | #BarçaEibar pic.twitter.com/3P8UV7Kz7e
Substitute Ousmane Dembele salvaged a draw for Barca 10 minutes later, although they are seven points behind leaders Atletico Madrid despite having played two games more.
Barca squandered a golden opportunity to take an eighth-minute lead, Braithwaite dragging his spot-kick wide after referee Javier Alberola Rojas had used the pitchside monitor to penalise Pedro Bigas for a foul on Araujo.
The Denmark international thought he had made amends shortly after the midway point of the first half, but his cool strike from Junior Firpo's cross was ruled out by VAR for offside.
Antoine Griezmann then pulled an effort wide from outside the penalty area as Barca went in at the interval having had just a solitary shot on target.
Dembele and Miralem Pjanic flashed strikes wide in the early stages of the second half before the former was denied by Marko Dmitrovic after being played clean through.
The Frenchman was made to pay for that miss when Kike picked Araujo's pocket inside the Barca half and coolly slotted past Marc Ande ter Stegen for his fifth goal of the campaign.
Dembele belatedly got the better of Dmitrovic in the 67th minute, firing home at the back post after Junior's cross flashed across the face of goal.
Francisco Trincao clipped narrowly wide of Dmitrovic's right-hand post in stoppage time as Barca missed the opportunity to make up ground on Atleti ahead of the leaders' clash with Getafe on Wednesday.