The only jewish NY baseball player at this time (that I know of) is Mets 1st basemen Ike Davis, His mother is definatly jewish, his father is not (Former Yankee Ron Davis) . I dont think he considered himself much jewish, but as it has become known to him that its a good idea to play the jewish roots, he has warmed up to the idea.
Anytime there is a potential jewish player in NY its well known because the teams want to promote to the jewish fans.
Ama’re Stoutamier of the Knicks might also be jewish. He has said there is jewish roots on his mothers side, but its been unclear exactly what that connection is