Fabianski saved spot-kicks from Gary Caldwell and Jack Collison to help Arsène Wenger's side to a first FA Cup final in nine years after a tense game against Wigan Athletic side had gone to a penalty shoot-out.
"I've got to give Lukasz all the credit to him," said Oxlade-Chamberlain.
"For someone that has been behind the brilliant Wojciech Szczesny this year, whenever he's played for us, he's been absolutely superb. He's the hero for us today. Full credit to him - he's an unbelievable professional."
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