The Hoops kick off their Conference League campaign against Bodo/Glimt on Thursday, February 17 and both players were included in the squad list handed into UEFA this week.
Postecoglou has stressed that their inclusion does not necessarily mean an imminent return to action for either, although Turnbull is closer to making a comeback.
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Hide AdAnd while the Celtic boss has been cagey over potential injury timelines, he offered a clue as to Furuhashi's progress, revealing the Japanese striker is "two or three weeks behind" his teammate.
"Just read into it that if they're fit and available they'll be in the squad," the Celtic boss said.
"Dave is obviosuly closer becuase his injury happened before Kyogo so he's probably two or three weeks ahead of Kyogo.
"I haven't put timeframes on it because I could end up being wildly out, but Dave is working hard, Kyogo is working hard.
"I expect to see Dave before Kyogo but in terms of Europe, they're both in the squad because hopefully they are available at some time for us."