Hawthorn's top draft pick in the 2020 National Draft, Denver Grainger-Barras hyperextended his knee while playing a practice match for Box Hill against Richmond.
The Hawks medical team are hopeful the talented defender has dodged serious ligament damage but will need scans to determine the extent of the injury.
Grainger-Barras was selected with pick 6 in the 2020 National Draft and was tipped to make his debut in the early stages of the season after an impressive preseason.
The 195cm defender was recruited from WAFL club Swan Districts and has been lauded for his intercept marking.
It was a horror day for the Hawks injury-wise as young defender Will Day sustained an ankle injury and was subbed out of the 29-point loss to Richmond at the MCG.