Morrison played with Giggs at Manchester United before joining West Ham almost a year ago.
Jarvis wrote in the Daily Mail: "When the club first signed Ravel I wasn't here, so the first time I got to see him was the start of this season.
"He did really well in pre-season, scored a few goals and shone, so the manager saw that and picked him in the first team.
"He's started extremely well, showing the skill he's got - for instance in the Spurs game with his solo goal. If he can keep playing well week in, week out, he'll be a real top player.
"He tries all different things and you just come to expect it from him. He's got great ability and he will keep improving."
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