KEY BISCAYNE Poland’s Agnieszka Radwanska used her wits to defeat world number two Maria Sharapova 7-5 6-4 to win the Sony Ericsson Open final on Saturday and once again deny the Russian.Sharapova has now lost all four finals she has featured in at the Miami tournament and all three she has played in this year.Radwanska’s victory was her second of the year following a triumph in Dubai and her ninth WTA title, arguably her most valuable one."I’m just very, very happy that I have been able to play my best tennis since the beginning of the year. Let’s hope that I can continue,” said Radwanska, who is aiming this year to push for a first grand slam title."I will never be able to serve like Maria but I try different things and mix it up,” she added.The Pole, ranked fourth in the world, won the tournament without losing a set and she showed exactly why with a classy display that left Sharapova scurrying around the court at times.There was characteristically little emotion from Radwanska, beyond a timid half-raising of her arms, when Sharapova went long on the final point to hand her victory.