Last year, Fruean underwent his second open-heart surgery and was picked up by the Chiefs after the Crusaders only offered him a wider training group contract.
The good news is Fruean should make a full return, and indeed the likes of Justin Collins (in rugby) and Rob Waddell (rowing) have done so after the ablation procedure.
Chiefs coach Dave Rennie, trying not to sound like a heart specialist, says there is a low risk of complications.
"There's a few confused signals in the heart. There's probably a fear that he's going to keel over - he's at slightly more risk than you or I at having a heart issue - but it's affecting his breathing and his ability to go full time," says Rennie, whose midfield and backline options are fast eroding.
Injured are Bundee Aki (shoulder, three weeks), Charlie Ngatai (calf, four to six weeks), James Lowe (knee, four to six weeks), and Robbie Robinson (probably season).
In the frame to suit up in midfield on tour are Andrew Horrell, Tom Marshall, Tim Nanai-Williams, Asaeli Tikoirotuma and Mils Muliaina, plus greenhorns Anton Lienert-Brown, who has bypassed the national under 20 trials, and Jordan Payne, Waikato out of Auckland, and big on potential if not experience.
Fruean has apparently received the latest frustrating news with a positive mindset. "He's a special character. We're going to altitude in a couple of weeks, but we're more concerned about him as an individual and he's more concerned about the team," said Rennie.
Fruean's ongoing heart issues previously hampered his play to such an extent that All Black coach Steve Hansen said he could not pick him due to an inability to play at intensity for 80 minutes.
This latest setback does nothing to alleviate concerns for New Zealand's centre depth behind Smith.
Fruean's eligibility is not open, as was supposed in some circles. He played for the 2009 Junior All Blacks.
The Chiefs leave Auckland today. They meet a resurgent Western Force in Perth on Saturday night before games in the republic against the Bulls and the Cheetahs.
On the plus side is the return from the sick bay of prop Ben Afeaki, flanker Sam Cane and halfback Augustine Pulu.
Chiefs squad
Squad travelling to Perth and South Africa:
Ben Afeaki, Gareth Anscombe, Sam Cane, Aaron Cruden (co-c), Michael FitzGerald, Josh Hohneck, Andrew Horrell, Tawera Kerr-Barlow, Tanerau Latimer, Anton Lienert-Brown, Jamie Mackintosh, Pauliasi Manu, Rhys Marshall, Tom Marshall, Liam Messam (co-c), Mils Muliaina, Tim Nanai-Williams, Jordan Payne, Augustine Pulu, Brodie Retallick, Mahonri Schwalger, Liam Squire, Matt Symons, Ben Tameifuna, Kane Thompson, Asaeli Tikoirotuma, Brad Weber.