Opal played for the Thunder during the team's championship-winning season and when she and a friend dragged Harriet along to the trials, she thought it was a joke.
"I guess that the joke is on me now as I'm playing in the team," she laughed.
Both play in different positions and will complement each other during the three round-robin match programme.
"We have an advantage in that we know each other's strengths and weakness and able to work through this.
"I feel the pressure as I'm confident in Opal's abilities and she has youth on her side, whereas I have experience."
Harriet admits they love to correct each other and have high expectations when one's not pulling her weight.
She said the team wondered about the Stratford pair's relationship and whether they enjoy playing together. But she treats Opal like any other team member on the court.
"As I'm an older player with experience, I'm more here to support the younger players to strive to their full potential as we have a very talented young squad with members who could one day represent New Zealand."
Also in the squad is Teghan Omelvena-Ngatai, who returns from last year. She was invited to the recent Steven Adams High School Invitation Camp and tournament in Wellington.
Joellen How returned from New York after she finished a scholarship at Wagner High School and was previously a New Zealand age-group representative.
Former Tall Fern Zoe Kensington will juggle both motherhood and dairy farming and Hannah Lee and Arna Bright were part of the under-17 and under-15 nationals held recently.
After winning the competition last year, campaign manager Rebecca Langton said the side has drummed up positive support from local businesses, including a new sponsor.
She said the aim is to make that leap up into the national competition.
"We are keen to rebuild and get ourselves back into the NBL division," she said.
In preparation for the tournament, the squad is training twice a week and developed their own style.
They will look to play a fast-paced game, have confident shooters and relentless defence, Langton said.
The team is coached by Josh Reeves.
Taranaki Thunder D-League draw:
Thursday, August 12: Taranaki Thunder v Northland, 2pm
Friday, August 13: Taranaki Thunder v Auckland, 1pm
Saturday, August 14: Taranaki v Harbour Cyclones, 9am
Sunday, August 15: Play offs from 9am, D-League final, 3pm (Sky Sport 8)