The Livingston hitman, 17, is on the Red Devils' radar as they plan for the future.
And he's hinted a move south of the border could be in the offing.
Knox told the Daily Record: "It was completely different experience to anything I have been used to. I was there was for a week and I trained with the Under-23s side and their manager is Nicky Butt.
"He's a legend and he really made an effort to put me at ease so I'll just wait and see what comes of it."