Lindelof, who arrived at Old Trafford in a £30m deal from Benfica this summer, started the European Super Cup against Real Madrid earlier this month, but has not featured in the Premier League this season.
First-choice pairing Eric Bailly and Phil Jones are both suspended for the game against Basel next month, however, and Mourinho has confirmed that Lindelof, in addition to Chris Smalling, will be given the chance to impress in that fixture.
"Eric is playing really well," Mourinho told reporters. "I have to say Smalling is in very good conditions and I have also to say Victor is improving every day.
"So, as you know, against Basel Jones and Eric are both suspended, so against Basel we will play Victor and Smalling and no problem at all. The squad is good and the mentality of the players is very good too."
Man United have won all three of their Premier League matches at the start of the new campaign.