Horne-Francis, who had foot surgery last November, was absent during the second half of Friday's trial against Adelaide.
The Power say the star on-baller reported "minor awareness" in a foot and was rested.
The dynamic 22-year-old, who fractured a foot in round 18 last season and had a plate removed in November, only rejoined full pre-season training in recent weeks.
Horne-Francis, the AFL's No.1 draft pick 2021, also missed Port's internal trial last week after copping a knock to a shoulder at training.
His fresh concern came after Greater Western Sydney's woes worsened with two players suffering hamstring injuries in a trial game against Collingwood.
Influential forward Brent Daniels and emerging utility Cody Angove both left the field in the second quarter of Friday's match against the Pies.
The extent of the injuries was yet to be known.
The Giants have copped big pre-season blows with star midfielder Tom Green to miss the entire premiership season after tearing the anterior cruciate ligament in a knee last week.
Dual All Australian defender Sam Taylor has been sent to a surgeon after scans revealed a significant hamstring injury.
Taylor was injured playing for Western Australia against Victoria in last Saturday's State of Origin clash and could need surgery.
The Giants are yet to put a timeframe on the brilliant backman's return but he will miss the early stages of the premiership season at least, with any operation meaning a longer stint on the sidelines.
Livewire Toby Bedford is also battling a hamstring injury, with the 25-year-old out of action for between four and six weeks.
And on-baller Finn Callaghan, who has a hip flexor injury, is in doubt for GWS's premiership season opener against Hawthorn on March 7.
The midfielder will miss all pre-season games but the club hasn't given up hope of him featuring against the Hawks.
The pre-season has taken a toll on other clubs, with Carlton's Adam Cerra to miss the early stages of the premiership season after damaging a hamstring in match simulation against Brisbane on Wednesday night.
Cerra has a history of hamstring issues - in 2024 he had five recurring hamstring ailments - and will be sidelined until at least after the Blues' bye in round two.
But Carlton hope vice-captain and defensive linchpin Jacob Weitering will be fit for their first premiership season game, against Sydney on March 5.
Victorian Weitering sustained a fractured rib against Western Australia.
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