The Tottenham centre back was substituted in the 81st minute during the 2-0 win against Manchester City on Saturday and Mourinho was not optimistic about his condition after the game.
In his pre-match press conference ahead of their Europa League clash against Ludogorets on Thursday: "He has a muscular injury but not as big as we initially thought.
"He'll have his time to be out but not like a month, which was immediately what we thought.
"So I would say between 2-4 weeks but of course not playing tomorrow."
"Erik I don't think back this week for tomorrow or for Sunday. I think I can say that."