Williamson (22) will bow out of the junior drivers' grade at the end of this month after racking up 153 starts to date in five seasons of driving.
New regulations allow junior drivers to drive a sixth season if they have fewer than 75 wins, but Williamson's success means he will be joining the open driving ranks next season.
He will be crowned the country's leading junior driver at the Harness Racing New Zealand awards next weekend based on his 70 wins this season, but there is unfinished business in the form of the junior drivers' championships.
Twice in previous years, Williamson has led going into the final heat, only to get pipped at the post.
However, his last drive, Zena Mac, looks to be his strongest drive, so Williamson hopes he will be the one making a late bid this year.
"You need three consistent ones, don't you - you need to be thereabouts in every race,'' Williamson said.
"Some of my horses are going to be roughies, but they're all drawn pretty well. Hopefully, that can help me a bit.''
Williamson knows plenty about his rivals in the first of the three championship heats, a c1-c2 handicap trot.
His father, Phil, has both The Silver Fox and Brads Kenny in the race on the 10m mark, but Williamson has drawn the Murray Edmonds-trained Yankee Commando who steps from six on the front line.
"He ran second to He's Like A Wind a few starts back, so he can run on his day,'' Williamson said.
"Hopefully, tomorrow night he feels like he can do it. Usually, you can get them away pretty nice from slightly wider on the front tapes. If he can make a quick beginning, that's a positive.''
Williamson drives Southland pacer Leah Mac in the second heat, and drawing behind the unbeaten Errol Finn could work in the pair's favour.
"She can run a good race on her day - she has rated 1.57 [for a mile] before,'' he said.
"If she showed up on her good form, it wouldn't surprise me if she could sneak into somewhere and finish in the top half of the field.''
Two top-four finishes might have Williamson in the hunt going into the last heat with Zena Mac, where he will look to land handy from barrier 1.
"There are no standouts in it, and I've drawn 1 which obviously helps, too,'' he said.
"There should be a bit of improvement in her. By the looks of the race, she should get the right run. If that happens, she would be a good chance.
"She's got the draw and she's going to be easy to drive - if she sits in the trail, turning for home, she should run in [the first] three.''
Williamson captains the South Island team of six for inter-island honours over their northern rivals.
Junior championship tips
South Island
Craig Ferguson
• Jean Sebastian (Race 4, No 2)
Stevie Golding
• Brads Kenny (Race 4, No 11)
Matt Anderson
• Donegal Jimmy Dave (Race 6, No 7)
Katie Cox
• Mighty Empire (Race 8, No 3)
Brad Williamson
• Zena Mac (Race 8, No 1)
Jessica Young
• Couldn't split her drives
