The Dutch-Moroccan was due back from a torn cruciate ligament this month but his return has been delayed by a groin problem.
El Hassnaoui, 26, missed much of last season due to ankle and groin injuries and then tore his posterior cruciate ligament in a friendly against Preston in July.
Hearts head coach Robbie Neilson said: “He should start back training next week and then we’ll build him up again. It’s been really difficult for him because it’s been one thing after another.
“Sometimes, when you’ve been out for a long time, you come back and there’s another area that’s a bit weak and you get small niggling injuries like this. We’re just trying to nurse him through it.
“This sort of thing happens to every player.
“They get a long-term injury and they focus on repairing the problem and then, when they’re back, something else goes. The groin is nothing major with Soufian, it’s just one of these things.”