PORT Adelaide forwards Jack Watts and Sam Gray are in doubt for Friday night's must-win encounter with Essendon at Adelaide Oval.

Both players were restricted to jogging laps and doing some run-throughs along the boundary line at the Power's main training session on Wednesday morning.

Watts completed the warm-up with the main group, while Gray was talking to assistant coaches before walking and jogging laps.

Superstar Robbie Gray was also on light duties, but that's not unusual for the three-time All Australian and club best and fairest as the 30-year-old is on a managed training program.

Watts took a knock to his left knee late in the first quarter of the Power's 51-point loss to Collingwood at the MCG last Saturday, but finished the game, compiling 13 disposals, six marks and a goal.

Sam Gray had 17 disposals and a goal, but the small forward has carried an ankle injury this season and missed the round 16 loss to Fremantle.

He was also dropped for the round 19 win against the Western Bulldogs, but had 40 disposals in the SANFL the following week to earn a recall in round 21.

Gray has kicked 21 goals in 18 games this season, while Watts has averaged a goal a game (18 from 18) in his first season at the Power.

The ninth-placed Power must beat the Bombers and hope Gold Coast pulls off a massive upset against Geelong at GMHBA Stadium on Saturday to sneak into the finals.