Torres made a premature exit from training on Monday and was absent as 25 members of the first-team squad took to the field at Chelsea's Cobham training base to finalise preparations for Wednesday's Champions League clash at Stamford Bridge.
Chelsea host Schalke, who they beat 3-0 in Gelsenkirchen last month with two goals from Torres, bidding to enhance their position at the top of Group E.
"Fernando we know has a muscular (leg) injury," Mourinho said. "We don't know the dimension. Scan tomorrow. Out for tomorrow and the weekend (against West Brom).
"After that it's the international break and we will see how he recovers."
Left-back Ryan Bertrand is also out of the Schalke contest after picking up an unspecified injury in training on Tuesday.
Four of the squad which trained on Tuesday morning were goalkeepers, while midfielder Michael Essien, who is not eligible for the Champions League squad, was also present.
Kenneth Omeruo, a 20-year-old Nigerian defender, trained with the first team and could come into contention.
The Blues responded from the opening loss to Basle at home by winning at Steaua Bucharest and in Germany to take pole position in the group and could take a significant step towards the knockout stages with victory against Schalke.
Mourinho hopes Chelsea can respond from Saturday's loss at Newcastle which ended a six-match winning run.
"When you win and win and win sometimes players forget why they win and they think they win just because they are good," he said.
"There are many other ingredients in football matches that make you a consistent winner."
Mourinho was angry following the Newcastle loss, but insists he was exaggerating when he said he had made 11 wrong selections.
"I've had lots of time to watch the game, to reflect about the game and I don't change my opinion," he added.
"(But) I don't want to see the changes I make tomorrow as somebody's paying for the defeat against Newcastle, which is not the case.
"It's simply that I read the game and I read it once, twice, three times, try to analyse the way the people perform.
"(And) try to make changes not to punish people, completely far from it, just to try to get the best team to win the game."