United opened their pre-season preparations with a 5-2 win over Los Angeles Galaxy on Sunday night, and the Red Devils will also face Real Madrid, Barcelona and Manchester City in friendlies during their time in the United States.
The club's first competitive match of the new campaign will also be against Real Madrid in the European Super Cup on August 8, however, and Herrera is already looking forward to the clash in Macedonia.
"Real Madrid in the European Super Cup? They are the strongest team right now, they've won the last two Champions Leagues, but a Super Cup final always motivates you. I'll be just as motivated. Of course, playing against Madrid is a good test for us," Herrera told reporters.
Real Madrid qualified for the European Super Cup after winning the Champions League last season, while Man United landed the Europa League title.