Lionel Messi put Barca ahead but second-half strikes from Darwin Machis and substitute Jorge Molina saw Granada produce an unlikely comeback, one that provides Atletico Madrid and Real Madrid with a huge boost.
Barca coach Ronald Koeman was sent off on a frustrating night for his side, who remain two points off the top.
Here are some of the players who stood out most on Thursday.
✔️ Antoine Griezmann: 7.7
It was a wonderful turn and a clever pass from Antoine Griezmann which set up the only Barca goal by Messi.
The France forward now has either a goal or assist in each of his last four outings for Barcelona.
In a solid performance he had 44 passes into the final third and two completed dribbles, while he also forced Aarón Escandell into a good early save with a long-range strike.
❌ Marc-Andre ter Stegen: 5.9
For the first goal from the visitors, Oscar Mingueza (6.6) was unable to cut out an accurate throughball from Granada's Luis Suarez.
That allowed Machis (7.0) to take one touch and deliver a cool finish under goalkeeper Ter Stegen - who was slow to react - while the positioning of Sergi Roberto may also be questioned.
The second goal game from Sergi Roberto's side of the pitch, with Molina losing Gerard Pique (6.6) and heading in a cross from Adrián Marín.
⭐️ Lionel Messi: 8.5
Despite defeat for Barcelona, it was Messi who emerged as the man of the match.
His goal was excellent, a move he started himself 25 yards from goal seeing him link up with Griezmann in a slick one-two before firing a low finish into the bottom corner.
It was a boost for Messi as he had failed to net in three of his last four league matches.
He could have scored again soon after when he was set up by Sergio Busquets, with that save from Escandell ultimately proving a lot more significant than it seemed at the time.
Messi was at the centre of everything for Barca, with team-highs for shots (6), dribbles (3) and final-third passes (59), but it is not a night he or his team-mates will remember fondly.