Powell is expected to join United in a £4 million deal.
Crewe's financial position means warding off any unwanted interest will be impossible and skipper David Artell gave a glowing reference ahead of what might be the teenager's last game for the club.
"He's the best player I have ever played with," said Artell. "He can go right to the very top and all of these Premier League teams are fully justified in watching him.
"We are not a one-man team but there have been games this season he has done things which are out of this world."