Torres suffered the knee problem shortly after being introduced as a substitute against Manchester United last weekend, but Mourinho has insisted that the Spaniard won't require surgery.
Asked how long Torres would be absent, the 50-year-old told reporters: "One month, three weeks. Something like that.
"It's not a surgery situation but it's not a little strain. It's a lateral ligament injury."
Torres has scored eight times in 23 appearances for the Blues during the current campaign.