Boric was a good All Blacks' lock - playing 24 tests - but hasn't worn the black jersey since the 2011 World Cup victory over Canada in Wellington and is nearing the twilight of his career due to the serious neck injury he suffered last year. May has been a good, but not spectacular, campaigner for the Crusaders, Chiefs and Hurricanes, playing more than 50 Super Rugby games in total.
Retallick, on the other hand, is one of the three top locks in New Zealand, along with Sam Whitelock and Luke Romano. He is a current All Black which means he is less likely to chase the money overseas, but, as we have seen with Richard Kahui, that's not necessarily a given.
Crockett, meanwhile, is in the All Blacks' squad but ranked below Tony Woodcock - though not on this season's Super Rugby form. The loosehead prop is also up against Ben Franks for competition at the top level. Game time for the All Blacks is not a given, yet he has decided to stick it out in New Zealand rather than go offshore and that is a significant result for the NZRU.
High-profile players such as Jerome Kaino, Sonny Bill Williams and Kahui have blazed a trail to Japan but the quiet and unassuming Crockett, 30, could play a similarly important role for the NZRU.
He makes a good case for persevering against the odds when it might have been easier to take the money.
After a demoralising test against Italy in Milan in 2009 in which Crockett was penalised off the park - wrongly according to then referees' boss Paddy O'Brien - he probably had every right to seriously consider his options overseas.
Following that European tour Crockett didn't play another test until 2011, a year in which he played three, but he failed to make the World Cup squad. Last year he played four more tests on the European tour.
Now he is proving a revelation for the Crusaders, who have always held him in high esteem. After Ben Franks' move to the Hurricanes, Crockett has been forced to cover tighthead prop, something he has never had to do in the past, and he is making an extremely good fist of it. With him there against the Stormers in Cape Town at the weekend following Owen Franks' injury, the Crusaders' scrum didn't take a backwards step.
He has always been good around the field as a defender and ball-carrier, but his workrate has gone to a new level this season.
While Woodcock's opportunities have been limited at the Highlanders due to a hamstring injury, All Blacks' coach Steve Hansen will be happy with the development of Crockett, Ben Franks and the two outstanding prospects at the Chiefs, Ben Afeaki and Pauliasi Manu.
In Crockett, though, Hansen and New Zealand rugby has struck gold, and, just maybe, an unlikely poster boy for perseverance in an age of instant gratification.
