So far this season he has 6 goals and in Palace's last season in the "Championship" he scored 28 goals (32 inc cup games). One of those at Ninian Park.
"We will have to wait and see the outcome of a scan Andy is having before we know the exact extent of the injury," Palace boss Iain Dowie told the Western Mail.
"But whether he is with us or not against Cardiff, we have to pick ourselves up and get ready for that game.
"We need to go to Ninian Park and get some points to keep us in the hunt with the teams moving towards the top of the Championship table.
"On Tuesday we faded towards the end of the game and let ourselves down.
"We can't afford to let that happen again against a Cardiff side who have achieved some good results recently."
Palace did not have Jobi McAnuff in their squad for the game against Reading so no news on whether he will feature against City.
Bluebirds Summer target Clinton Morrisson is set to start upfront on Saturday for the Eagles.