Westerman, 24, burst on to the scene in 2007 at the age of 17 with Castleford and was tipped as a future England international.
He hasn’t quite made it to the top level yet, but impressed as Hull fell just short against Warrington on Sunday, going down 18-16.
Radford said: “Joe Westerman was outstanding, the best player on the pitch by a country mile. If he continues this form, he’ll be on for a real good season. He’s dropped 5kg since Christmas and really ripped it up in training.
“His ability is something we’ve spoken about as a group. Potential is probably a word that is used time and time again when you describe Joe’s career, and if he can continuing the form he’s showing, maybe we’ll stop talking about potential, and he’ll reach the level where he’s as good as he can be.
“He’s been fantastic for us so far, especially in the first half last week.
Westerman joined Hull ahead of the 2011 season and has gone on to score 186 points in 80 appearances in the black and white.