Don't panic. Do not panic. Nothing has collapsed. Nothing is doomed. This is not a Manchester United transfer exploding in a cloud of incompetence and regret.
According to the Guardian's Jamie Jackson, the reason Marcos Rojo's move to Manchester United form Sporting hasn't yet been confirmed by the club -- despite the player himself having announced on Argentinian radio that he was on his way -- is down to the complicated contractual position in which Rojo and Sporting find themselves. There is a tangle of third-part ownerships that need to be resolved, and until that happens he remains a Sporting player.
However, the Guardian's information is that the proposed loan move of Nani in the opposite direction is not "considered a stumbling block". which means everybody can stop worrying that the move might fall to pieces once Sporting's doctors establish that United's departing winger has, in fact, no brain.