Inside the pages of her book she has written down tips from past games and has also set out everything she wants to focus on during each quarter of the up-coming match.
"It might just be something that I noticed in the last game and I want to carry it through," she said.
This book has stayed with Sinclair for years and has become something of a motif during her two seasons playing in the ANZ Championship.
Sinclair, who turned 20 yesterday, is playing in her second play-offs campaign with the Magic today.
Unlike last year, she has played almost every game this season in the midcourt and will be better prepared for the 2015 play-offs.
The winner of today's knockout match between the Magic and Steel will progress to the semi-finals to be played in two weeks time.
Magic will go into the game as firm favourites with the Steel only managing three wins from 13 games this season.
Such is the new play-offs system - and the dominance of Australian teams in the ANZ Championship - that the Steel have still managed to scrape into third place in the New Zealand conference, handing them a play-offs spot.
The Magic have also lost more games than they have won this season but managed to finish second in the New Zealand conference.
Sinclair said, despite the Steel's modest record, they would not be taking them lightly.
"We did that last week and it definitely did not go well," she said. "I think we just have to play a really clinical game."
She said it was a big goal for her team to make the semis.
"This is why we play, to make the finals, and I think that's the goal for every team to make the semi at least, so it will be a tough game but I think we have it in us."
Sinclair added it was a great honour to be named to trial for the Silver Ferns next month, but at present her entire focus was on the Magic.
By making the play-offs this year the Magic have become the only side to make the finals for eight straight seasons. Sinclair said it was a great achievement.
"We don't think about [that record] too much, but we know what has happened in the past and there is a bit of pressure to keep that record alive."