Play Impact represents the average difference in final placement (1st-8th) between players who played a plain copy of a minion and players who did not.
For example, if
- Players who play a copy of minion X usually place 4th
- Players who do not play a copy of minion X usually place 5th
It would mean playing this minion improves the final placement by 1, and therefore this minion's Play Impact would be '+1.0'. It is important to note that a minion's Play Impact can change drastically based on which turn it was played, which composition that player was using etc.