The Spain international was set to start in Chelsea's Premier League clash with Tottenham on Saturday, but was replaced by Samuel Eto'o after injuring himself in the warm-up.
Eto'o went on to score the opener as Chelsea romped to a 4-0 win which leaves them seven points clear at the top[ of the Premier League.
Torres has struggled with injury problems this season with thigh and knee issues already having ruled him out for sections of the campaign.
Mourinho expects the 29-year-old to be out of action once again, but the full extent of his injury will not be known until the result of scans.
"Torres has a muscular problem," he told the club's official website. "And even when they are small it is always a couple of weeks.
"He has to go for scans.
"He's already had two problems, in both knees, both ligaments, but his recovery was faster than we expected.
"He also had a little muscular problem and now he's having another one.
"Sometimes it happens. There are other players who have the same. Others have a complete season without problems."
Torres has only scored five goals for Chelsea this season, with fellow forwards Andre Schurrle, Eto'o and Eden Hazard all scoring more.
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