Sylvan Ebanks-Blake has left United to join newly-promoted Championship side Plymouth Argyle for an initial fee of 200,000 pounds.
The 20-year-old striker had been at Old Trafford since July 2002, but found himself hampered by a broken leg in February 2005.
Despite fighting back from the injury and rediscovering his finest form for Rene Meulensteen's Reserves, Blake only made one first-team appearance last season - scoring in the 4-1 Carling Cup win over Barnet.
Delighted Pilgrims boss Ian Holloway admitted to the club's website: "I'm very, very pleased. He's someone I have been monitoring for some time. I almost had him on loan last year.
"He's got power; he's got pace; he's hungry to make a reputation. He will be a threat to opponents when we have got the ball and when we haven't - so, defenders, 'Watch out!'
"I am as excited about having him here as he is about coming. I looked him in the eyes when I met him and I am convinced he is someone eager to succeed and who, in my opinion, is as honest as the day is long.
"I just want to help him become the player I believe he can be. He isn't there yet, but he can get there."