Southgate has included Rashford in the senior squad for Saturday's World Cup qualifier against Scotland and a friendly against France on June 13.
"He has had to think about what's best for England and for me as a player," Rashford said. "I'm happy to be with the seniors and to continue my development. It's important to be on the same page.
"It's something you look forward to, being selected for your country ... Whatever age group you're called upon it's important you have a mindset where you're going to achieve great things.
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"To me it's not being fast-tracked. There's been a lot of games; England and United have dealt with it in a positive way."
(Reporting by Aditi Prakash in Bengaluru; Editing by Peter Rutherford)
