The Manchester United defenders were injured on England duty and Mourinho did not sound optimistic either will be back in action any time soon.
Smalling has a knee injury, while Jones has has a toe injury caused by his club and country colleague during an England training session last week.
Asked about the prognosis for Smalling and Jones, Mourinho said: “They are long-term injuries.
“They [the injured players] are not important. The important ones are the ones who are ready to play , that’s the way we have to think we cannot be here crying or speaking about the players who are not available to play.
“You know that Zlatan and Ander Herrera are suspended, that Herrera is two matches ban for that episode against Chelsea. You know what happened in the English national team with Smalling and Jones, you know we have also Paul Pogba injured.
“But, I repeat, they are not important. The important players are the one who are ready to play, the ones I trust and the ones who are going to give everything tomorrow to try and keep us in the fight for the top four.”
Mourinho confirmed skipper Wayne Rooney, missing for the past three weeks, is available to feature against West Brom at Old Trafford tomorrow.