Shanklin has not played since suffering a knee injury in the Magners League clash versus Aironi rugby in January.
The two-time Grand Slam winner was originally expected to be out of action for three months and was targetting a return before the end of the season.
But following further scans Shanklin has admitted his season is over and he faces a battle to play again.
"My knee is in pretty bad shape really and so I'm just going to see how I recover," said 70-times capped Shanklin.
"I'm not going to play again this season. I'm going to make sure my knee is right and I'll take it from there. It's quite a serious injury I've got."
Shanklin's career has been blighted by knee problems and he is also out of contract in May.
But Shanklin insists he is not worried about his contractual situation, only focusing on recovering from this latest injury.
"It's not something I'm really focusing on too much," said Shanklin.
"I mean my knee is pretty bad. I want to get that right. And if I get my knee right, I'll get a contract."
During seven seasons in the Magners League with Cardiff Blues, the veteran centre has racked up 62 appearances and touched down 18 times.
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