Te Anau-born Sun beat eighth seed Qinwen Zheng 4-6, 6-2, 6-4 in just under two hours in the first round at Wimbledon, easily the best result of her career.
The lakeside town of Te Anau has about 3100 residents, but tennis club president Greg Sheppard said it had nearly 120 members, about 80 of which were juniors.
"It’s quite the thriving tennis community. It’s really competitive," Mr Sheppard said.
"We have a fulltime coach now, which has really helped."
Sun was raised in Switzerland from the age of 5, where she completed her school education
Mr Sheppard said although Sun travelled the world and had a "host of great coaches", she had returned to Te Anau for invitational tournaments or "just to hit a ball around".
"I remember she once played a tournament against our top senior players when she was 14 — they all left with their tails between their legs.
"She was really good from a young age."
Sun switched allegiance from Switzerland in March and is the first New Zealander to make a grand slam singles main draw in seven years.
She needed to win three qualifying matches to achieve the feat, with Marina Erakovic the last Kiwi to do so when she played her 28th and final grand slam tournament in 2017.
Sun's only prior experience of a grand slam was a first round exit at this year's Australian Open, when she was still representing Switzerland.
Mr Sheppard said Sun was a "really nice" person.
The last time Sun played a major tournament in Te Anau was in 2019, when the then-17 year-old, representing Switzerland, defeated Suzy Larkin in the $1000 invitational match.
"It’s exciting for our little town. We're all buzzing from the coverage of her win at Wimbledon.
"But it’s also great news for New Zealand tennis."
In the next round, Sun will play against Yulia Starodubtseva from Ukraine, who also came through qualifying. — Additional reporting RNZ
