After missing the past two games due to injury, Alvarez started against Mallorca.
But the striker was substituted in the 61st minute, visibly disgruntled, after missing the clearest chance of the match: a penalty saved by goalkeeper Leo Román.
DAZN cameras captured him sitting on the bench, bitterly commenting, "Always me," likely referring to being substituted again and having played just one full match in five games this season.
Alexander Sorloth came on in his place, but was sent off a few minutes later.
"Alvarez is our best attacking player, he's confident on the ball," Simeone explained after the 1-1 draw. "He was having a great game, but I felt it was necessary to bring on Sorloth to create more depth in the penalty area.
"Unfortunately, the sending off left us with ten men, and like all players, it's natural for him to get angry when he leaves the pitch."