Alonso did away with those concerns from day one. Mbappe has started every single game for Madrid thus far, and played all-but 16 minutes of Los Blancos' perfect start to the season.
Nominally, he has operated as a striker, but Alonso has been flexible in the way he has used him. Indeed, the manager relies heavily on positional play, asking his side to fill individual tasks within a position. Against Osasuna, in the first week of the season, Mbappe played much like a traditional striker - staying mostly central, and offering a run off the last defender when Madrid had a chance to hit on the break. He grabbed the only goal in a slightly unconvincing 1-0 win.
But he has filled other roles, too. Against Espanyol, he started up front with Garcia. It seemed a confusing set-up. But instead of having two alongside each other, Alonso used Mbappe as a second striker of sorts, linking play and working in coordination with the midfield.
"Today he played in a more different role, as a playmaker," Alonso explained after the game. "We talked about the responsibility he had to be closer to Urko (Gonzalez de Zarate). On (Marko) Dmitrovic’s long balls, that superiority was important. Kylian understands football very well. Today in his role, in a different position, as a second striker, he did very well."
It would perhaps be a bit premature to dub Mbappe a "complete striker". There is a long way to go on that front. But his improvements are clear to see.