Kirwan's uncertainty mirrors that of many rugby union commentators who doubt Marshall has the range of skills to be successful in rugby union. While Marshall is both brilliant and talented and quickly became a star of the NRL after making his debut for Wests as a teenager in 2003, he has always battled major deficiencies in his game.
Marshall is a notoriously weak defender and lacks the length in his kicking game which would be essential for a rugby union fullback. He also joins the Blues at a time when his league career is in decline.
The New Zealand-born five-eighths was one of the highest-paid players in the NRL but he has struggled this season to hold a starting place in a Wests team which has been unable to fight its way off the bottom of the premiership ladder.
For many observers, his move to rugby union appears to have come too late for him to be an effective, long-term signing. Instead, Marshall's signing for what some media outlets have reported could be up to $500,000 a season is seen as a commercial move to try and win new fans to the Blues in Auckland, which is a rugby league stronghold.
Marshall has insisted throughout his protracted negotiation with the Blues that he is serious about making a success of a move to rugby. He has indicated he has ambitions to play for the All Blacks or for the New Zealand rugby sevens team at the 2016 Olympics in Brazil.
"Based on what (John Kirwan) has told me about the winning culture the Blues are working to create and where he sees my part in that, I'm really looking forward to this next stage of my sporting career," Marshall said in a statement.
Kirwan said he was excited to have secured a player of Marshall's ability.
"It has been bit of a process because it's obviously a big decision for Benji," he said. "But he's really excited about the challenge and we're thrilled to have someone with his professionalism and ability in the organization. I think it's going to be a great journey for us all."
Further questions have been raised about the decision to recruit Marshall because the Blues' most glaring weaknesses last season were among the tight forwards and they have yet to sign anyone in that area.
They also need a top-class first five-eighths and Kirwan made a strong effort to sign the young All Black Beauden Barrett who announced on Friday he is staying with the Wellington-based Hurricanes.
- AP