The prevailing view on Marshall would appear to be that he is high-risk and a player who could prove valuable for the Blues but not, at this juncture, the All Blacks.
Without financial support from the NZRU, the Blues are going to have to dig deep into their coffers and rely on third party agreements if they are to make Marshall a credible offer.
Marshall is estimated to earn A$700,000 ($819,000) a year at the Tigers and while his agent Martin Tauber has said in recent weeks that his client is willing to take a pay cut, it's difficult to believe he would be willing for that to be over 50 per cent.
Under the collective agreement, franchises can pay a maximum of $180,000 to any player - which is mostly everyone bar regular All Blacks. The NZRU tops up their contracts and those of any other player deemed to be worth more than that for whatever reason.
The question for the Blues is how much they are willing to spend on one player - given the impact it will have on their ability to recruit in other areas, such as lock, prop and centre where they have an obvious need for reinforcements.
Realistically they are probably going to have to stump up anywhere between $300,000 and $500,000 to be in the hunt for Marshall, who is also talking to the Waratahs and Japanese clubs.
Reports from across the Tasman suggest the Waratahs would be willing to allow Marshall to supplement his income by playing in Japan in the Super rugby off-season. It is possible, too, that the Australian Rugby Union may be interested in topping up the Waratahs offer as they have a dearth of resources at first-five, although the Tigers' five-eighth has also been touted as a possible rugby fullback.
Allowing Marshall similar dispensation to play in Japan should he join the Blues would be problematic as there is an expectation that contracted Super rugby players in New Zealand will be available to play ITM Cup.
The other concern for the Blues is that their flirting with Marshall may dissuade Barrett from leaving the Hurricanes.
The 22-year-old is understood to be seriously contemplating a shift to Auckland on the basis that he'd be the man around whom the franchise builds their team.
If the Blues were to make a considerable investment in Marshall, that would surely complicate the picture as far as Barrett is concerned and leave him less certain about the role he would be asked to play.
The final loose thread that isn't likely to be easily tied is the idea Marshall could have a tilt at the Olympic sevens in 2016.
Sevens coach Gordon Tietjens has confirmed anyone wanting to go to Rio will have to be available for most of 2016 - ruling them out of Super rugby contention.
Blues coach Sir John Kirwan yesterday said he had not heard anything since he spoke to Marshall's manager a few weeks ago but he was intrigued at his decision to leave the Tigers.
