Spurs, who visit Fulham on Thursday night, will play six fixtures in March before many of their players face triple-headers with their countries.
The Spurs boss has been managing the minutes of Harry Kane and Gareth Bale but the captains are pivotal to England and Wales, respectively, while Colombian Davinson Sanchez and Argentine Giovani Lo Celso could be called up by nations currently on the Government's ‘red list’, which would require a period of quarantine on return.
"I am concerned but there is nothing in my hands that I can do, nothing at all," Mourinho said.
"When they go to the national teams, they're not our players. Then they belong to the national teams. Then they belong to the national coaches. Everything is out of our hands.
"I have concerns at every level. Not just the Covid level, or the red list or travelling abroad, I have also concerns of other areas, but let’s wait, let’s see what’s going to happen."