Morrison scored an early contender for goal of the season on Sunday during West Ham's stunning 3-0 win at Tottenham.
The 20-year-old picked the ball up inside his own half and sprinted past Michael Dawson and Jan Vertonghen before expertly lifting the ball over Hugo Lloris.
Even though he only cost around £1million, many thought Sam Allardyce was taking a huge gamble by signing Morrison from Manchester United in February 2012.
The midfielder has had disciplinary problems in the past. He admitted two counts of witness intimidation and he was also fined £7,000 by the Football Association for a homophobic tweet just weeks after his move to Upton Park.
A 12-month loan spell at Birmingham appears to have turned Morrison from boy to man, however, and Tomkins is optimistic that his team-mate can go on to achieve great things.
"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," the West Ham defender said.
"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.
"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."
Morrison has scored four goals in eight games so far this season for the east London club.
His fine early-season form has led to a call-up to the England Under-21 squad - the feeder team for the senior side.
Tomkins is sure that Morrison will be able to deal with all the hype that comes his way this season, and the defender has no doubts about the 20-year-old's talent either.
"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," the 24-year-old said.
"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."
Morrison's performance in a 'false nine' position up front has allayed fears that West Ham will not be able to produce enough goals this season without the injured Andy Carroll.
The impact on morale within the squad and among the West Ham faithful will also be huge, Tomkins reckons.
"It was a massive result for us," said Tomkins, a born and bred West Ham fan himself from Basildon.
"The fans were singing non-stop. The win was for them because to be honest we haven't done too well away from home this year.
"To win 3-0 at White Hart Lane is massive. For them it doesn't get much better than that.
"They have been brilliant for us and as a local lad myself, I know how massive it is for us."