Marshall, running at both first-five and fullback for the Blues as they get set for their first pre-season game on February 1, has been given the tick of approval by former All Blacks coach Henry.
"He's starting to feel comfortable in the group which is good," Henry said in an interview published on the Blues website. "It's the first time he's used the ball in rugby ... since he was a kid so it's going to take him a while to get into the rugby mentality rather than the rugby league mentality.
"He's a mature guy, he's professional, he's played a lot of professional football and he's pretty fit. He's worked very hard on his fitness because he arrived here in November not that fit but he's made huge strides in that direction and he's starting to get a feel for the game.
"That's going to take a while and he needs to play some rugby for that to happen but that will happen and I'm encouraged by what I see."
Coach John Kirwan said this week Marshall was progressing in the 15-man game, but was mindful of the differences to league.
"I said to him the other day, rugby league can be one dimensional sometimes," Kirwan said. "Everything's in front of you, everyone's running forwards or backwards, whereas in rugby union everything is three dimensional because you've got different angles. But he's a quick learner... he's been more excited about the challenges than anything else."
Henry said his role at the Blues had changed slightly this season.
"I'm still doing the defence with Grant Doorey ... but I'm also doing the leadership this year which I've never done before so that's stimulating. I'm trying to help them develop as good leaders and help with the individual development of people."
The squad began training last week after their Christmas break, with Henry saying he was pleased with the start the team had made.
"It's been a really positive week, there's been a lot of hard work done," he said.
"There's some clarity on roles and a lot of work done on skill development and working on guys' skill level which is going to be key during the year."
