Hopper was subbed out of the match in the second half, however was seen with a limp in the opening term before further concerns were raised in the third quarter.
Young forward Judson Clarke was brought into the game in place of Hopper, who will undergo scans on Saturday to learn the full extent of the calf complaint.
"He'll miss some time. Not sure how long, but hopefully not too serious."
Defender Daniel Rioli sustained a suspected ankle injury in the second quarter of the match and underwent treatment in Richmond's rooms before returning to the field.
Hardwick noted that the pacey half-back, who was one of the Tigers' best performers against the Cats, should be fit to face Essendon next Saturday night for the annual Dreamtime clash.
Richmond will be hoping to have both ruckmen Toby Nankervis (ankle) and Ivan Soldo (foot) available for selection for that match, while forward Maurice Rioli jnr could be in the mix as he looks to overcome a hamstring injury sustained in Round 6 against Melbourne.