Now there is only uncertainty. And he does not need reminding of the Ben Afeaki case. His old Sacred Heart schoolmate had to pull the pin on rugby earlier this year on the heels of 12 months of pain, discomfort and frustration after the symptoms from a bad concussion never cleared enough for full contact.
"If I'm exerting myself at high intensity, there's a little bit of nausea... I can work up to about 160 heart beats per minute. If I keep it there or thereabouts I can train with no symptoms. That's what I've been doing lately, keeping a level of fitness but not overdoing it, so when my return comes I'm not too far behind the eight ball," says Polwart.
Still hopeful there is time to play some part in Auckland's campaign, he would need to be symptom-free very soon, as then there will be the road back to match fitness. In the meantime, his Varsity teammate Mitch Karpik and the tigerish Blake Gibson have got their hands on that No 7 jersey, so a path back into the loose trio is far from clear.
Polwart is philosophical about his rugby future, and life after rugby is high in his thoughts.
"It's something I've had to think about because of the nature of how long it's been. I can't completely dismiss (retirement) because that's the nature of this type of issue. I've put some time into my life after rugby, but also my main aim is to return. I'm feeling about 75-80 percent, so it's about getting over that hill."
The coaching has given him a focus while he continues his rehab.
"At the moment, I'm really enjoying it. It's good being a hybrid, in between a player and a coach. I have taken the role of defence after Xavier had to leave and I've learned a lot from the coaching side of things. I'm learning about life as a coach. It can be pretty frustrating."
Auckland have conceded 232 points in their seven games, ranking them the fourth most parsimonious defence in the Premiership, and sixth overall in the ITM Cup. Don't judge Polwart solely on that, though.
"We've been pretty unlucky with some of the tries we've conceded this year through intercepts and driving mauls. But I think the boys are reacting well. We're seeing some great improvements from individuals with their tackle rates."
Sounds like he is far less exasperated, then, than Auckland's 2004 defence coach Frank Bunce, who wondered aloud why players could stick to a defensive system at training and then when the heat went on during a game, all his tuition would go out the window.
Polwart leads the defensive review post-game and works alongside the loosies giving them tips. During games, he is the waterboy, passing on the coach's message and adding his own advice.
"There's that fine line. I don't want to completely dismiss myself as a teammate alongside them, but hopefully they respect me as a coach."
It is clear that Auckland coach Paul Feeney, a fan of Polwart the player, is fast growing to be an advocate of Polwart the coach.
"He's gold for us. A guy in his situation could feel sorry for himself and not turn up to every training. But he's here the whole time, defensively he's taking clips and talking to players individually. His knowledge of defence and rapport with the players is awesome," says Feeney. "He's taken a massive leadership role in this group, half as a player and half as a coach. He's the new hybrid."
The new hybrid he may be, but Polwart has no contract, Super or provincial, for 2016.
"That's not my main concern at the moment. It's about getting my health back and setting new goals after that."
Good luck to him.
*An in-form Auckland challenge for the Ranfurly Shield on Thursday night against the Magpies. They have not held it since 2008, well before even Sean Polwart, from a long line of quality No 7s in the blue and white hoops, was on the provincial scene.
