For the goalie who had the highest defensive success rate in the postseason of 2011, what's his legends ID ?
Post season of 2011 refers to year = ’2011’
defensive success rate refers to (SUBTRACT(1 (DIVIDE(PostGA/PostSA)), *100%)

SELECT T2.legendsID FROM Goalies AS T1 INNER JOIN Master AS T2 ON T1.playerID = T2.playerID WHERE T1.year = 2011 ORDER BY 1 - CAST(T1.PostGA AS REAL) / T1.PostSA DESC LIMIT 1