#1 Robert Lewandowski
Robert Lewandowski is Poland's captain, their leading goal-scorer of all time, and scored 16 goals in qualifying - the first time that has happened in the European level of qualification. It is safe to say he is Poland's most important player, and to an extent, he is Poland itself.
After winning nearly everything at Bayern Munich (except the CL, but apparently Real Madrid has a monopoly on it), Lewandowski has set his eyes on newer, richer adventures in foreign lands, and his agent has seen to it that everyone knows.
With the WC, Lewandowski has the best possible platform to show his prospective employers as to what he brings to the table - goals, goals, and then some more goals. With Milik, Zielinski and Blaszczykowski around to deliver the passes to him, Lewandowski has no reason to be worried about on that front.
The worry for him today will be the Senegalese defender called Koulibaly, and all 195 cms of him. Lewa's biggest strength is in the air, and unfortunately that is also what Kalidou's favorite area to defend. The battle between these two should make for an interesting view, and the winner of that will decide the winner of the game.