Atletico Madrid need goals. That is why they signed Luis Suárez, and although Simeone has suggested that the Uruguayan could start, it is most likely that he will opt for Costa, Joao, Correa, and Carrasco. For that reason, he spoke to them for a long time after training.
Simeone summoned the four, presumably the four attacking players who will be in the starting eleven against Granada, and gave them the talk. This is what 'AS' calls, 'la cholina'.
It isn't the first time that Simeone has done this. In fact, it is a regular thing. It all depends on the match, and if it has any added importance, like this one being their first of the season in La Liga.
The four, sitting on the grass surrounding their coach, listened to his talk, surrounded by his assistants. What he said stayed between them. We will soon see if it has any effect.