What if during the Battle of Grunewald, the Teutonic Knights saw the Lithuanian retreat for what it was - a false retreat - and rather than pursuing instead focused on the Poles. Assuming the Knights - including the ones which in OTL pursued the Lithuanians - focused on the Poles and crushed them, killing the king, before engaging and also defeating the returning Lithuanians in good order.
How would this affect the course of European history?