But he has revived his career in a year-long loan at Birmingham and is now in Sam Allardyce's first team.
Tomkins said: "Last year, mentally - and he will probably vouch for this - he wasn't quite ready and the gaffer put him out on loan at Birmingham.
"He got great experience there and he did very well. That set him up to come back to us.
"Whenever I have seen him in training and playing he has been excellent. He has got his chance and to be fair, he has taken it.
"He has matured from last year and hopefully, as an English person myself, he can get better and better.
"Off the pitch he is a lot more focused. Obviously he is a young lad moving from up north down south.
"I suppose he found it hard. He has always had the ability but he has got it right all round now."
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