Marcus Rashford struggling for goals this season
Rashford enjoyed a stunning breakthrough season at Manchester United last term – scoring eight in 18 appearances – but has failed to carry over his form.
The 19-year-old has found the back of the net just seven times in 40 outings under Mourinho and is without a Premier League goal since September.
But Mourinho insists the Red Devils academy product needs support rather than criticism and has no problems with his professionalism and dedication to improve.
Jose Mourinho offers encouragement to Marcus Rashford
"We have people that are not [taking their] opportunities and that's bad for the team," Mourinho said.
"But I speak with them because when you give absolutely everything and you leave the pitch absolutely dead of work, that's fine for me.
"Marcus Rashford doesn't score goals since September [in the Premier League] – the only thing he deserves is support. Nothing else.
"Support, no critics, support. He works, he works, he works. He tries, he plays through the middle, he goes to the left, he goes to the right, he tries, he tries, he tries.
Marcus Rashford without a Premier League goal since September
"The kid is desperate. It's not a surprise for me – the second year not being as good as the first one.
"Maybe one day I will try to find out if it happened with Ryan Giggs or someone. They appear as a kid and then the next year it's not the same.
Get Quotes on Home Insurance
"But the kid is phenomenal – an amazing professional. So no problem. I told him – keep going."