"Jack and James have really come on this year in terms of their physical attributes but also their knowledge of playing - just simply by training with the first team every day," he said.
"They are two lads who work really hard so it is great credit to them that they have forced their way into the squad and to the bench and in Jack's case got on at Arsenal. They are two good young players who are the future of our football club and will hopefully improve even more."
Keen also had a word of praise for left-winger Kyel Reid, telling whufc.com: "Kyel has been in and out, played for the first team and come back out. Hopefully he will keep improving and again be another asset for the future."