The midfielder faces four weeks out after breaking down while away with Argentina.
Joaquin said, "I've seen him in bad shape. He was coming off another setback at Betis and he's screwed because an injury is always a setback, but we hope to recover him as soon as possible.
"He's a very important player for us. But we have a great squad, so we have total confidence."
Joaquin also stressed that the season has just begun and acknowledged that the defeat against Sevilla was painful.
"This has only just begun, it is clear that losing a derby always hurts, but we have total confidence in the team and in the coaching staff. There is a very long season ahead and we have a great squad.
"This is very long, there will be complicated situations, because it is increasingly difficult to win, but I have no doubt that the team will continue to respond and compete," he added.