And yet Sanchez also have off days without Giroud being involved.....Different roles is exactly the point. When Giroud starts Sanchez is forced wide and his productivity drops markedly. When Giroud is on the bench Sanchez either plays up front or plays with a CF who allows him to drift inside (Welbeck/Walcott). In both situations he is far more productive. It's hardly surprising - the stats tie in with both common sense and what we've seen on the pitch for 3 seasons.