Morrison has hit the headlines in recent weeks after a few eye-catching performances, most recently scoring an early contender for goal of the season to help the Hammers record a memorable 3-0 win over Tottenham Hotspur at White Hart Lane.
The 20-year-old had question marks over his discipline when he signed for the Hammers from Manchester United last year, but Tomkins believes that he has matured as a player now and could go on to great things if he keeps his feet on the ground.
"Last year, mentally - and he will probably vouch for this - he wasn't quite ready and the gaffer made a decision to 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 and whenever I have seen him in training and playing he has been excellent," Tomkins told PA.
"Off the pitch he is a lot more focused now. He has matured a lot. For a young lad moving from up north down south it can be hard. He has always had the ability but he has got it right all around now and hopefully that can continue. He is still a young lad so you've got to take it easy because all this hype is going to come out about him, but if he keeps level-headed he can go anywhere. He could go to the top level.
"He's gone from strength to strength and he keeps getting better and better. He is fully deserving of his Under-21 call-up. He proved again in this match what he can do at the top level. Hopefully he can keep improving because he is a talent. Technically, he is one of the best I have seen in training. There are not a lot better for an English lad at his age."
The result lifted West Ham up to 13th in the Premier League table with eight points from their opening seven games.