With their finals campaign on the line, it was a bitter blow for Port against a struggling Carlton outfit who went on to a 110-106 win for their first victory of the season.
Gray was taken from the field on a medicab and didn't take any further part in the match.
After initial concerns about the injury, Gray was seen sitting with the reserves later in the match.
How many weeks will Gibbs get for this?
Ouch - Robbie Gray's been stretchered from the field after this heavy tackle from Bryce Gibbs #AFLBluesPower http://t.co/noSNQMH3mA
— AFL (@AFL) June 20, 2015