Smith initially injured his groin in the second JLT Series match against Brisbane and has not been seen in 2019.
"We've attempted to rehab Joel's groin conservatively and it wasn't really making a lot of progress, so we felt we needed to back off his running for a period of time," Misson said.
"We're going to have another good crack at conservative management in two or three weeks' time, hoping that the period of off-loading has helped that area heal.
"What that means is he won't play again this season. Our aim is to really get him up and going for pre-season next year."