The 28-year-old is midway through his projected recovery after an operation to release a nerve which was being pinched by a bulging disc.
He has resumed some light exercise with swimming and cycling dominating his recovery programme, mixed in with some running which he has to be more careful about because that pounding can stir up his stiff neck.
Faumuina noticed a problem during the Super 15 when he started to lose strength in his left arm during extended training sessions.
"The nerve was being compressed and they did some scans and found out about the problem in my neck. I could still play with it, it wasn't sore but when I got in the gym I was losing strength.
"Once they found out it was a bulging disc, I missed the last few games to see if it could recover."
Faumuina had a cortisone injection to improve his strength and range of movement but there was little change so he was booked in for surgery.
There were several options - one which gave him a shot at the World Cup or another which would take him out of rugby for six months and park his tournament ambitions alongside the injured Aaron Cruden and Patrick Tuipulotu.
Surgery went without complication but there was no guarantee when or if the damaged nerve would fire up again. The optimistic view was for a six week recovery period before Faumuina could test his rugby fitness during the ITM Cup campaign and push for a World Cup place.
"They say the strength could just come back any day, quite abruptly and it will start firing up again," Faumuina said. "A lot of guys have this sort of thing but for someone who plays in my position it is a little more of a problem."
Meanwhile the All Black selectors picked Nepo Laulala as tighthead backup to Owen Franks for last week's test in Samoa and they also have Ben Franks and Ofa Tu'ungafasi in the enlarged squad for Friday's test against the Pumas in Christchurch.
"It seems to be going alright. It's a procedure which they've been doing for a while now and we'll find out if in a few weeks if it's any good," Faumuina said.
"Where the nerve comes out of the disc in your spine, I had some keyhole surgery to make a bit more room for the nerve to move around. I've got to take it easy for a while, it was quite stiff after the operation.
"It's bad timing and fingers crossed.
"I've also got to think long-term because they want to get rid of this so it doesn't bother me later on."
- Wynne Gray
