Croker has not played since suffering a head knock in Manly's loss to Canberra on May 3, and has been battling inner-ear and neck issues.
The Sea Eagles have desperately missed his control and toughness, giving up a lead to the Raiders after he went off and losing three of four games since.
Croker will again be on the sidelines for Sunday's mid-table clash with St George Illawarra at 4 Pines Park, but the signs are improving for the 27-year-old.
He stepped up skills training at Brookvale in recent days, and is expected to commence contact work next week.
Coach Anthony Seibold conceded next Saturday's clash with the Rabbitohs could come too soon for the hooker, but was lifted by Croker's return to training.
"There's been a lot more non-contact skills. Next week my understanding is he'll do a bit more contact," Seibold said.
"We miss Crokes. He's a real heart and soul of our group. It's been concerning for him.
"But the welfare of the player comes first. We want to make sure that he's received the right treatment. It's a go-slowly approach."
Jake Simpkin was brought across from Wests Tigers a fortnight ago, as cover for Croker and to replace the outgoing Karl Lawton next year.
He could come into the side to face the Dragons on Sunday.
As a junior at Brisbane, the dummy-half represented Queensland at under-18s while Seibold was at the Broncos, in a side that also featured Reece Walsh and Sam Walker.
"There was this crew of kids coming through and he was in that crew," Seibold said.
"They had success as juniors. I followed him from afar. I just like what he brings - a really good work rate, but he's also very skilful.
"He's 22 years of age and played over 40 games. It's been a real tough slog for him in those 40 games because he has been in and out of first grade a bit."
Seibold confirmed Haumole Olakau'atu would play, after the second-rower shrugged off a calf injury to boost his chances of keeping his NSW jersey.
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