Brian To'o suddenly departed the field midway through the second half of the NRL grand final.
The Panthers star was seen walking down the tunnel at Accor Stadium as his team continued their tireless battle against the Storm.
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Channel 9's Danica Mason reported that To'o suffered a suspected knee injury.
Mason later described the incident as "nasty knee clash".
He did not return for the remainder of the clash, although he had already made a significant impact on the match.
To'o ran for 213 metres and recorded five tackle breaks in just 58 minutes as the Panthers went on the claim their fourth straight premiership.
