Torres, who led the line for the Blues in Saturday's defeat to Newcastle at St James' Park, has undergone a scan to determine the severity of a muscular injury.
Samuel Eto'o is expected to start up front against Schalke in the Spaniard's absence as Chelsea look to extend their lead at the top of Group E.
"No, he is out," Mourinho confirmed on Tuesday when asked about Torres's chances of playing.
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"Fernando has a muscular injury. We don't know the dimension but we await the scans but tomorrow [he is] out and out for the weekend too. After that comes an international break. Let's see if he can recover after that."
Torres's injury will also keep him out of the Premier League clash with West Brom on Saturday and Mourinho has called on Eto'o and Demba Ba to make the most of any opportunities they get as a result.
"[Ba and Eto'o] want to play and they are waiting for opportunities to play," he remarked, "so, when they have that chance and they know they are going to have it in this game and the next game at West Brom, I think it has to be a good motivation for them.
"Hopefully, they can express on the pitch the way they work during the week."
Torres has been in impressive form of late, scoring twice against the Bundesliga side at the Veltins Arena before netting the winner against Manchester City at Stamford Bridge.