It's perfectly justified to have concerns, don't you think?
He's coming after a meh season, to a new and very demanding league, and will be asked to do a lot of dirty work on top of running our play. I'm not even so sure he's the right guy for current United team, not because I doubt his quality, but because there is a huge effort required from our midfielders to cover for all forwards. Maybe that will change, but too many "maybe's" for me to feel confident.
Like I said, I will trust ETH on this one.