The Spain international has been a maligned figure since joining the Blues and was not even part of Mourinho's squad to face Leicester City on Saturday, where Diego Costa bagged his second Premier League goal and Didier Drogba made a short cameo in the 2-0 win.
The 30-year-old striker has been linked with a transfer before the window closes, but, despite his lack of involvement at the start of the campaign, Mourinho is keen to keep him.
When asked if Torres would be leaving, the Portuguese replied: "No. I want three strikers in the team and I can’t do the season without three."
Mourinho was then asked what Torres would need to do to in order to earn a place in the first team, to which he replied: "He has to score more goals than the first [striker]."
Torres watched on as compatriot Costa, who also usurped him in the Spanish national team, struck his second goal in English football's top-flight, a tally it took Torres 17 games to reach.
Despite his struggles, the former Liverpool forward had been linked with a return to Atletico Madrid and, more recently, as a potential replacement for Anfield-bound Mario Balotelli.
Mourinho, though, only has three strikers at his disposal after purging his squad of the forwards he criticised last season, with Romelu Lukaku joining Everton for €36 million, Demba Ba leaving for Besiktas and Samuel Eto'o departing on a free transfer.