Both players have been involved in legal cases in Spain, with Sanchez being sentenced to 16 months in prison for tax fraud, only to avoid actually going to jail as first-time offenders are not incarcerated in Spain if the sentence is less than two years.
Herrera, meanwhile, has become embroiled in a match-fixing row regarding Real Zaragoza's 2-1 win over Levante in 2011, although he vehemently denies any involvement in the incident under question.
However, Mourinho suggested that both will be available for this weekend's match against Newcastle United, while Zlatan Ibrahimovic may also feature having returned to first-team training.
When asked whether Sanchez and Herrera had seemed distracted, Mourinho told reporters: "No. No, the squad is good, everything is fine.
"Eric Bailly, Daley Blind, the two players that are out. Zlatan started training with the team two days ago, so two days with the group and improving. We are fine."
United take on Newcastle at St James' Park on Sunday looking to make it seven wins from eight games so far in 2018.