Veteran St Kilda midfielder Lenny Hayes was knocked out and stretchered from the field early in Friday’s AFL practice match against Collingwood.
Hayes was trying to tackle Tyson Goldsack at Visy Park when he suffered a blow to the head, which appeared to be accidental contact.
He immediately dropped to the ground and play was stopped for several minutes while Saints medical staff attended to the onballer.
The 32-year-old missed nearly all of last season with a knee reconstruction.
He made his comeback at the start of the pre-season competition.
This weekend marks the last round of AFL pre-season games.