Ross Lyon will hand over the Fremantle coaching reins for tomorrow's NAB Challenge match against West Coast at Arena Joondalup.
Lead assistant Peter Sumich will be on control of the Dockers' line-up for the pre-season clash.
Fremantle football manager Chris Bond said the shift was made to give Lyon a new view of his team and to help the development of his deputies.
“This continues our work in helping to develop all of our coaches,” he told the club's website.
“By having one of our assistant coaches in the chair, it will give Ross a different perspective of the game."