Incoming Wallabies coach Ewen McKenzie doubts whether Benji Marshall could adapt quickly enough to make a big impact as a rugby union playmaker.
In a sign the Australian Rugby Union is unlikely to target Marshall's signature, McKenzie felt the Wests Tigers five-eighth might have left his run too late to be a star in the 15-man code.
Marshall, 28, has been linked to Super Rugby clubs Melbourne Rebels and the Auckland-based Blues after announcing he wants to leave the Tigers at the end of the NRL season and possibly play for the All Blacks.
While the NSW Waratahs have played down talk they could sign the Kiwi international, Queensland mentor McKenzie warned he didn't possess the instincts required to be a game-breaking rugby playmaker.
''I don't doubt the competitiveness; I don't doubt the athleticism; I don't doubt the skill. It's more about where the instincts are,'' said McKenzie, who starts as Wallabies coach next month.
''That determines how successful you are going to be.
''The older you are, the more entrenched you are with the instincts of whatever you've been doing and the harder it is to suddenly go and develop new instincts.''
McKenzie rated Marshall an X-factor talent like mercurial Reds No 10 Quade Cooper but questioned whether he'd adapt to less space available in rugby's phase attack.
''These players do well because they don't think about things - they just do it,'' he said.
''It's like changing gears in your car. The space in rugby and the space in rugby league is different.
''The good players can learn but it's just a question of how long they take; how long the investment is before you get the return.
''My experience is that the older the guy is, the harder it is to make the transition.''
Rugby's most successful league converts have been outside backs with Israel Folau, Lote Tuqiri, Jason Robinson and Mat Rogers largely playing in the back three, while Rogers had four seasons before he played No 10.
Sonny Bill Williams also produced his best season at inside centre in 2012, his third full year in the code.
NSW assistant coach Alan Gaffney indicated there might not be room in the Waratahs' backline if they retained Folau and signed Wallabies teammate Kurtley Beale.
''Obviously if we get certain other individuals (Folau and Beale) to come on board, whether there's a balance there for him to even fit into the Waratahs is a debatable issue,'' he said.
McKenzie admitted he spoke with Marshall's manager, among many others, when he was coaching the Waratahs last decade as NSW tried to fix their Achilles heel.
''Trying to find someone who could play at 10 was a real challenge,'' he said. ''In the end, I went and hung around St Joseph's and waited for Kurtley to finish school.''
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