Boosted by his excellent performance against the Pumas in Napier after he replaced Whitelock in the first half, Thrush's story is one of perseverance and hard work. After being named in the match-day squad to play Australia in Wellington last year but failing to get on the field, he must have thought his chance to play a test on his home ground in front of friends and family was all but gone.
Blues player Tuipulotu quickly overtook him and Crusader Dominic Bird also appears set for the long term, but with the pair recovering from injuries - Tuipulotu is on the reserves bench after a lack of recent game time - it is Thrush's turn to have his time in the spotlight.
"He's a bit of a Steady Eddie old Thrushy, isn't he?" coach Steve Hansen said this week.
"And Steady Eddies either stay that way or they get comfortable in the environment they're in and actually become better players and I think that's what he's done.
"He's the complete team guy and it couldn't have happened to a better bloke. He's worked really, really hard on his game. ...
"[Whitelock] is a big loss. He and Brodie have been a combination that's been ticking along pretty good but one man's misfortune is another man's opportunity and Thrushy's got an opportunity. [Blindside flanker] Steven [Luatua] probably got an opportunity because of it as well. I'm picking both of those guys will put their hands up. That's the way it is with us. You come in here and pull the jersey on and you're expected to play well."
The Boks present a uniquely physical challenge, but Thrush showed enough against a huge Pumas pack that he is capable of not only performing his core roles in the lineout and scrum but also offering a fair bit around the park. His work on defence, especially, was impressive.
"It took me a long time to get here and when I got here it kind of took me back a little bit, if I'm honest. By [last year's] end-of-year tour I felt quite comfortable, or as much as you can," he said. "You're always on your toes, but this year I thought when I got my chance I'd just come in and go for it."
He has it at last and he laughed this week as he remembered his false start in the Bledisloe Cup test at Westpac Stadium last year, a 27-16 victory for the All Blacks.
"There were a few people [friends and family] who got to watch a good game, but just didn't get to see me come on. But they saw me warm up. They'll get to see me warm up but then run on this week."