Walkinshaw Andretti United is set for an all-new Supercars line-up in 2020 as Scott Pye will exit the team at the end of the season.
Pye joined WAU at the start of 2017 on a three-year deal and returned to the Holden fold for the first time since his debut season with Lucas Dumbrell Motorsport in '13.
Pye's exit will bring an end to a WAU spell that included the first victory of the WAU partnership at Albert Park last year en route to seventh in the championship.
He is now set to join Team 18 alongside Mark Winterbottom, in a move that could be announced as soon as tomorrow.
"I have really enjoyed my time at WAU and have developed some really close relationships with the crew, so the decision to leave is one I have not taken lightly," Pye said.
"Though we would have liked more, we have shared some great success together.
"I am excited by the new opportunity in front of me, and I'd like to wish WAU all the best for the future and look forward to racing against them next season and beyond."
Pye's current WAU team-mate James Courtney has already announced his move to a new Sydney-based team for 2020.
With two WAU seats up for grabs, Mostert is expected to fill one of the vacancies.
"Scott has been a great member of this team for the last three seasons," said Ryan Walkinshaw.
"I personally will never forget that win around Albert Park as the sun set, and I'm sure many others won't either.
"It was great to share his first win with him, and our first as Walkinshaw Andretti United. We wish him all the best in the future.
"As for our 2020 driver line up, the wait is nearly over, it won't be long now until we can share the exciting news."