After two seasons at Arsenal, Silvestre moved to Werder Bremen on a free transfer. He two seasons in Germany before being released on a free this summer. Two weeks ago he had a trial with West Ham and now he’s back at United.    

What's so "hell" about this? 
He gets world class training. I'd love that. :D

I think he will stay and play for  us :(

dude calm down. He just goes to his old clubs to keep in shapeuntil he finds anew gig. Je was atArsenal a few weeks before. Clubs like Arsenal and sometimes United allow their old players hospitality. Its called having class. I wouldnt worry about him getting in your first team.