PORT Adelaide coach Ken Hinkley has thrown the gauntlet down to recalled forward Jack Watts to cement his place in the side, while declaring it was an easy decision to bring back defender Darcy Byrne-Jones after serving a club-imposed one-week suspension.

Watts and Byrne-Jones are two of four changes to the Power line-up for Saturday's encounter with a dangerous St Kilda at Adelaide Oval.

All Australian candidate Tom Jonas returns from a hamstring injury, while pacy forward Aidyn Johnson comes in for his third game of the season, replacing Sam Gray who could miss more than one week with an ankle problem.

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After coming across from Melbourne at the end of last year, 27-year-old Watts played the first 11 games of the season for the Power before the 2008 No.1 overall draft pick was dropped for the 10th time in his career.

But a couple of impressive performances in the SANFL has earnt Watts his place back in the team ahead of youngster Todd Marshall, who had five disposals and two goals in last week's 21-point win over Carlton.

"Jack's opportunity is now in front of him to own the spot," Hinkley said.

"Toddy, over the last couple of weeks, hasn't been quite at the level he would expect of himself.

"Jack was never too far away, just some of his contest stuff we wanted to see get a little tighter on."

Hinkley believes Watts and Marshall are capable of co-existing in the same team, despite both playing similar roles in the Power's attacking structure.

Byrne-Jones' spot in the side isn't in question.

The small defender was dropped for the first time since making his debut in round three, 2016 when he was late to a training session last week.

"Darcy's played 56 games in a row before he went out, so he's a pretty important player," Hinkley said.

"If you talk about defender importance, he's right at the top with blokes we like to have in the side."

Byrne-Jones comes into the side for Jasper Pittard, the club taking a cautious approach with the 27-year-old, who has a history of hamstring injuries.

Gray is also sidelined with an ankle complaint he's carried for the past couple of weeks, and there's no guarantee the Power's second leading goal-kicker with 19 goals this season would be back next week.

"There comes a point where you need to put a break in that and get him right," Hinkley said.

"We're going to try and do that now, and he may only miss the one week.

"If it has to be more than that, it has to be more than that."

A fifth straight win for the Power would move them into the top four, but Hinkley knows the 15th-placed Saints can't be taken lightly after their outstanding victory over Melbourne last Sunday.

"Their willingness to take the game on was really clear," Hinkley said.

"Knowing (Saints coach) Alan (Richardson) a little bit, you'd suggest they would continue on that path and give us some real challenges."