Tomkins has been impressed by how Morrison has performed following last season's loan at Birmingham City.
"He's changed in the space of a year," Tomkins told talkSPORT. "When he first came here he had to mature and he went away to Birmingham and did that and he has come back a different player and person.
"If he keeps learning and keeps improving, like he seems to be doing, then the sky is the limit. He's a very talented player."
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