Prestia came off first with a hamstring problem, while Bennell limped off shortly afterwards with a calf complaint.
Both players will be scanned in the next 48 hours after the swelling has subsided to determine the severity of the injuries.
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Hamstring problems plagued Prestia early in his career but he has played 42 of a possible 44 games over the past two seasons.
While the extent of his injury is unknown, Suns football manager Marcus Ashcroft said Bennell's scan was more precautionary.
"We are confident he will only miss a few sessions," Ashcroft said.
Earlier in the session, Bennell won a 2km time-trial – the same test Prestia took out on the opening day of training earlier this month.
