Entering this match, manager Tata Martino had a real problem on his hands. Every center-back save for Javier Mascherano, who is a converted midfielder himself, was ruled out due to injury, meaning picking a back line would be tough.
Martino had several options he could take.
Adriano could once again feature as a center-back, as he has done a few times with relative success. His pace would have also helped against Granada's quick strikers.
On the other hand, Martino could have elected to go with Alex Song, who was originally brought to the club to feature as a backup for Busquets and a center-back if absolutely needed.
Martin Montoya could have even slotted in on the right of the center-back duo, as he has experience there in his formative years.
Yet Martino chose to start Sergio Busquets alongside Mascherano. Granted, Busquets is a defensive player and has slotted in at that position before, but it was the choice that made the least sense.
With Busquets at the back, there was absolutely no defense in front of the back line. Granda's goal came from Barca having no protection and it was clear that this was a bad choice.
Playing Busquets at the back wasn't the big mistake, it was not giving the defense any coverage. Martino could have put Song alongside Mascherano, but instead he chose to take the most important midfielder in the team out of midfield.
This decision could come back to haunt the Catalans. Had Busquets played in the midfield, then buildup play may have been more fluid. There are a lot of ifs after a loss like this.