Skipper McCusker and Turnbull haven't played since Wales took on Argentina at the beginning of November after they suffered knee and ankle injuries respectively against the Pumas.
Fellow Wales cap Shingler missed Saturday's Heineken Cup defeat at Exeter thanks to the groin problem he picked up against the same opposition a week earlier.
"We hope to select Shings and Josh this week, which adds to the depth in that area," Easterby told Walesonline ahead of the Cardiff Arms Park clash in Round 11 of the RaboDirect PRO12.
"We have suffered a bit and have had to ask (second row) George (Earle) to play out of position. It is something he has been prepared to do for the team, but it is not fair on him.
"We are nearly back up to full strength there, which is good in this period.
"Rob is hoping to be back in training on Christmas Eve. He will be available for the Ospreys, although he won't have had a huge amount of rugby going into that game."
A popped rib cartilage means hooker Ken Owens definitely won't feature against the Blues, although he could join McCusker in pushing for a place against the reigning PRO12 Champions.
The Scarlets still don't know when Morgan Stoddart might return again as he continues his recovery process following a lengthy lay off with a double leg fracture.
Stoddart made his long-awaited comeback in October but he has been out of action since the superb away win over Munster late last month.
"It is unfortunate because Ken was going really well and made a big impact with his ball-carrying last Saturday," added Easterby.
"It will be disappointing for him having been on the bench for a couple of weeks.
"Hopefully, he might recover for the Ospreys game, but we won't know that until nearer the time.
"We wanted to give Morgan a period to recover from a bit of stress in his lower leg. He is doing okay, but we will know more in the next couple of days.
"He came back and looked really sharp, but then had a couple of games and struggled with the amount of training and game management was an issue, so we took the view to offload him a little.
"Ultimately, the decision will come down to the medical team, who have worked really hard with him, and Stodds himself."