The three-test series started in Christchurch this week with New Zealand and England prevailing yesterday.
The second five-day test tomorrow sees the Kiwis host Australia at Marewa Croquet Club while England and the US face off at Te Mata Croquet Club in Havelock North.
The third and final test will be staged at Mt Maunganui, where the New Zealanders will host England and Australia will trade shots with the US.
"We have a good chance of winning. It's a close series but on paper England are our closest rivals," says Westerby, after New Zealand crushed the US 14-1 and England overwhelmed Australia 14-4 in the best of 21 matches.
Based on the first test results, New Zealand should eclipse the Aussies, and England the Americans, although previous New Zealand teams have looked across the pristine greens to find themselves in a mind swamp as England prevailed.
"We are careful not to be fixated on them as we've done probably in the past when we've fallen over," the 39-year-old says, before the four countries play nine doubles matches and a dozen singles with each player committing to three doubles and two singles.
The New Zealand line-up includes players who have all had shield experience.
They include Greg Bryant, of Wellington, Paddy Chapman, of Christchurch but now living in England, and Toby Garrison, of Wellington, the New Zealand Open winner.
Westerby reckons not too many of his teammates are looking too far ahead in terms of career.
"There's probably some unfinished business, perhaps because in 2000, against the form book, New Zealand ended up running England down to the wire.
"In fact it came down to the last game in the last match of the last test. I guess the addiction runs quite deep so it's hard to imagine we won't play again."
Hamilton-born Westerby, who attended Hamilton Boys' High School, started playing croquet when he was 12 thanks to his grandmother, the late Trixie Westerby, who was pivotal in asking a seasoned player to coach him.
"We [Westerby and his granny] went on to play a number of doubles tournaments together over my playing career so it was very special for me, especially when I won the New Zealand mixed doubles titles on two occasions [in 1994-95].
"I was very close to my grandmother and a reason was the connection we had in the game with an interest and passion that we shared."
His grandma had an enviable mental fortitude, possessing "a very strong single-ball shot".
"That was very handy in doubles competition which I can use to our tactical advantage."
His grandfather, the late Ronald Westerby, who became a Kiwi in his mid-50s, had a strong sporting background.
"He, in fact, was offered a professional contract to Warrington but in his time, obviously, the war affected his playing career.
"He always regretted not playing the game earlier but over a few years he was quite an able player."
That trend is common with youngsters in the code.
In 1994 Aaron Westerby, now 39, became the the New Zealand Open champion, something he attributes to his OE in England where competitions were second to none.
He actually saw some test matches between New Zealand and England where the latter established their dominance.
"It was a great record and [England] had three core players who underpinned that dominance," he says, adding that Chris Clarke was in the team.
His parents, June and Bryce Westerby, now retired in Katikati, always supported him but didn't play croquet.
"They very rarely watched me play," says Westerby whose former school supported him, too.
"It was something that was different but when you have an activity you fully engage in and get results ... then success fuels a greater interest," he says.
A great croquet attribute for Westerby is its shelf life relative to other codes.
"It's an amateur game with a very long apprenticeship," he explains, adding one can only grasp certain aspects tactically with more game time.
Despite taking breaks, Westerby found the code didn't desert him, enabling him to return to the fold with aplomb in relatively quick time.
"I guess I've been playing intensely for the past four or five years so as you get older it's a little harder to have those breaks," he says, emphasising it can vary with individuals.
His partner, Macushla Howell, of Auckland, isn't "quite a croquet player yet" but she and her daughter, Olivia, 8, will watch them on the final day for the first time in Mt Maunganui.
He doesn't expect that to be a distraction.
With 15 playing days plus travel days and tournaments, preparing and gaining selection for the shield tests does put some pressure on the demands of a young family life, something Garrison feels he can relate to.
