A gas turbine assembly comprising an axial fuel staging system, the assembly including a combustion zone defined in part by a sleeve assembly, said AFS system comprising: a primary fuel injector; and a secondary fuel injector downstream from the primary fuel injector comprising: a manifold; a housing coupled to said manifold and mounted to the sleeve assembly at an opening defined in the sleeve assembly, said housing defines an interior chamber therein; and a nozzle positioned within said interior chamber, said nozzle comprising an array (230, 300) of mixing tubes (232, 302, 400) that each comprise a proximal end, a distal end, and a perforated body including a plurality of perforations (246, 314, 402) extending therebetween, said proximal ends coupled in flow communication with said manifold and said perforations (246, 314, 402) of each body in flow communication with said interior chamber to facilitate discharging a mixture of fuel and compressed gas from said distal ends; wherein said array (230, 300) comprises a plurality of rows (248, 312) of said mixing tubes (232, 302, 400); and wherein said mixing tubes (232, 302, 400) in a first of said rows (248, 312) are offset relative to said mixing tubes (232, 302, 400) in a second of said rows (248, 312). a primary fuel injector; and a secondary fuel injector downstream from the primary fuel injector comprising: a manifold; a housing coupled to said manifold and mounted to the sleeve assembly at an opening defined in the sleeve assembly, said housing defines an interior chamber therein; and a nozzle positioned within said interior chamber, said nozzle comprising an array (230, 300) of mixing tubes (232, 302, 400) that each comprise a proximal end, a distal end, and a perforated body including a plurality of perforations (246, 314, 402) extending therebetween, said proximal ends coupled in flow communication with said manifold and said perforations (246, 314, 402) of each body in flow communication with said interior chamber to facilitate discharging a mixture of fuel and compressed gas from said distal ends; wherein said array (230, 300) comprises a plurality of rows (248, 312) of said mixing tubes (232, 302, 400); and wherein said mixing tubes (232, 302, 400) in a first of said rows (248, 312) are offset relative to said mixing tubes (232, 302, 400) in a second of said rows (248, 312). a manifold; a housing coupled to said manifold and mounted to the sleeve assembly at an opening defined in the sleeve assembly, said housing defines an interior chamber therein; and a nozzle positioned within said interior chamber, said nozzle comprising an array (230, 300) of mixing tubes (232, 302, 400) that each comprise a proximal end, a distal end, and a perforated body including a plurality of perforations (246, 314, 402) extending therebetween, said proximal ends coupled in flow communication with said manifold and said perforations (246, 314, 402) of each body in flow communication with said interior chamber to facilitate discharging a mixture of fuel and compressed gas from said distal ends; wherein said array (230, 300) comprises a plurality of rows (248, 312) of said mixing tubes (232, 302, 400); and wherein said mixing tubes (232, 302, 400) in a first of said rows (248, 312) are offset relative to said mixing tubes (232, 302, 400) in a second of said rows (248, 312).