PORT Adelaide will break with tradition and appoint co-captains for the first time in the club's history.

Midfielder Ollie Wines and key defender Tom Jonas are set to be named joint skippers of the Power for the 2019 AFL season.

The decision will be announced on Thursday.

Wines, 24, and Jonas, 28, replace long-time captain Travis Boak, who stood down at the end of last year after leading the club for six seasons since 2013.

Port Adelaide, even dating back before the AFL era, has never had co-captains since the club was founded in 1870.

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The decision also means it's likely the No. 1 guernsey, traditionally worn by Port Adelaide's skipper, won't be used this year.

Wines is expected to remain in the No.16 jumper while Jonas will wear No.42.

Boak will revert to the No.10 that he wore for his first six seasons from 2007-12.

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The announcement won't go down well with Port Adelaide's members, the majority of whom wanted the club to retain a sole captain when the issue was discussed at the Annual General Meeting earlier this month.

Wines, who is in doubt for the start of the season after dislocating his shoulder in a water skiing accident last month, and Jonas have both committed to the Power long-term.

Wines signed a four-year contract extension midway through last year until the end of 2022, while Jonas penned a new three-year deal in December, also until the end of 2022.