A gas turbine combustor comprising: an end cover; a combustion liner; an aft frame; at least one fuel nozzle extending between the end cover and the combustion liner, wherein the combustion liner extends between the at least one fuel nozzle and the aft frame; an outer sleeve spaced apart from and surrounding the combustion liner such that a cooling flow annulus is defined therebetween, wherein the combustion liner defines a combustion chamber having a first combustion zone downstream from the at least one fuel nozzle and a second combustion zone downstream from the first combustion zone; a fuel injection assembly disposed downstream from the at least one fuel nozzle, the fuel injection assembly comprising: a fuel injector having end walls spaced apart from one another and side walls extending between the end walls, wherein the end walls and the side walls collectively define a first opening for passage of air, wherein at least one fuel injection member is disposed within the first opening and extends axially between the end walls, and wherein the fuel injector terminates at a radially inner surface; a boss fixedly connected to the combustion liner and extending radially through the cooling flow annulus to a flange portion positioned at the outer sleeve, the boss defining a second opening that provides for fluid communication between the fuel injector and the second combustion zone, characterized in that the radially inner surface of the fuel injector is sealingly connected to the flange portion of the boss such that the first opening aligns with the second opening; wherein the combustor further comprises a support plate that couples the flange portion of the boss to the outer sleeve. an end cover; a combustion liner; an aft frame; at least one fuel nozzle extending between the end cover and the combustion liner, wherein the combustion liner extends between the at least one fuel nozzle and the aft frame; an outer sleeve spaced apart from and surrounding the combustion liner such that a cooling flow annulus is defined therebetween, wherein the combustion liner defines a combustion chamber having a first combustion zone downstream from the at least one fuel nozzle and a second combustion zone downstream from the first combustion zone; a fuel injection assembly disposed downstream from the at least one fuel nozzle, the fuel injection assembly comprising: a fuel injector having end walls spaced apart from one another and side walls extending between the end walls, wherein the end walls and the side walls collectively define a first opening for passage of air, wherein at least one fuel injection member is disposed within the first opening and extends axially between the end walls, and wherein the fuel injector terminates at a radially inner surface; a boss fixedly connected to the combustion liner and extending radially through the cooling flow annulus to a flange portion positioned at the outer sleeve, the boss defining a second opening that provides for fluid communication between the fuel injector and the second combustion zone, a fuel injector having end walls spaced apart from one another and side walls extending between the end walls, wherein the end walls and the side walls collectively define a first opening for passage of air, wherein at least one fuel injection member is disposed within the first opening and extends axially between the end walls, and wherein the fuel injector terminates at a radially inner surface; a boss fixedly connected to the combustion liner and extending radially through the cooling flow annulus to a flange portion positioned at the outer sleeve, the boss defining a second opening that provides for fluid communication between the fuel injector and the second combustion zone, characterized in that the radially inner surface of the fuel injector is sealingly connected to the flange portion of the boss such that the first opening aligns with the second opening; wherein the combustor further comprises a support plate that couples the flange portion of the boss to the outer sleeve. the radially inner surface of the fuel injector is sealingly connected to the flange portion of the boss such that the first opening aligns with the second opening; wherein the combustor further comprises a support plate that couples the flange portion of the boss to the outer sleeve.