Thunder livewire Daniel Sams has been cleared to play in Wednesday's Sydney derby at Manuka Oval, although the Sixers are still likely to be without speedster Ben Dwarshuis.
The left-arm quick, who has taken 11 wickets this season, is still nursing a groin injury suffered in last week's heavy loss to the Scorchers in Perth.
Sams, meanwhile, has missed the last two matches for the Thunder with concussion after being struck on the helmet by a short ball last Monday, but is expected to return in Wednesday's blockbuster.
"He'll be in the line up, it was a decent hit but he felt ready to go for the last game, protocols prevented him from playing," Thunder captain Callum Ferguson said.
"He's ready to go, had a hit yesterday, felt great, looking forward to him coming back."
Sixers captain Daniel Hughes was hopeful Dwarshuis would be fit for Saturday's match against the Hobart Hurricanes, also in Canberra.
The in-form 31-year-old, who has led the Sixers to the top of the Big Bash table as a stand-in captain for Moises Henriques this season, was also hopeful two of the team's biggest stars would return in time for finals.
Henriques and paceman Sean Abbott have been inside the Australian cricket team bubble all summer, on standby should there be an injury to someone in the Test squad.
"I'm not sure how it's going to work, we might see them the last couple of games before finals but we'll see how that pans out," Hughes said.
"They've got one more Test left and they need those guys to stay in the hub for concussions replacements and all that sort of stuff.
"That's what we've spoken about all year, trying to get ourselves in the best position at the back end of the tournament because we might get some handy players back.
"As long as we keep doing the right things and we can stay around that top two at the top of the ladder then we might potentially get those guys back for finals. Fingers crossed we do and we keep performing well."
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Hughes has clubbed 264 in nine matches so far this BBL, and has been a huge contributor to the Sixers' title defence.
"It's been really nice to spend some time and get some scores, just the group that I have around me and the batting order that I've got, it gives me the confidence to go out there and play with freedom," Hughes said.
"We've got [Dan] Christian at six and Carlos [Brathwaite] at seven, and some explosive guys at the top.
"Everyone's just playing with a lot of freedom and they're playing with clear minds when they go out there. We've got the batting there to get the runs that we need."
Early betting markers have marked the Thunder as slight favourites, and Ferguson was expecting a typically tight tussle.
"The Sixers have been outstanding the whole tournament, we know it's going to be a big challenge for us and we're really looking forward to that," Ferguson said.
"There's a lot of Sydney siders that reside here so no doubt there'll be plenty of green and plenty of pink out there. It's generally a really close contest as well between the two teams, we've had some really great clashes over the last few years."
Wednesday: Sydney Thunder v Sydney Sixers, 7.15pm at Manuka Oval