McLean will play just his fifth AFL game this year, lining up at the SCG against the Western Bulldogs on Friday night as injured teammate Joel Amartey's replacement.
Amartey is expected to miss at least 10 weeks after suffering a partial tear to an Achilles tendon in the Swans' 43-point loss to the Brisbane Lions last round.
If his recovery tracks exactly to the 10-week mark and Sydney hold on to finish in second, Amartey will miss the club's qualifying final following the new Wildcard round.
It is a setback for the 26-year-old, who has battled through numerous soft tissue injuries since arriving at Sydney in 2017 to feature in all 15 games so far this year.
McLean will be out to make the most of Amartey's absence, last playing at the elite level in round 14.
The fringe forward has maintained his form in the VFL, kicking six goals in the club's 133-point drubbing of Sandringham last week.
The Bulldogs (9-6) are eighth after winning five from seven matches before last week's bye, while the Swans (12-3) are second.
"He played really well in the VFL after we got the news on Joel, so he didn't know beforehand," Cox said.
"He played a really good game. He'll come into the team this week.
"We've got extreme confidence and trust that when he comes back into the AFL system, he'll do his role really well."
Well aware of Amartey's race against the clock, Cox said the priority for the key forward was simply being diligent in his rehabilitation.
"It's too far down the track to worry about that (finals)," Cox said.
"We're in a position where we've still got to qualify for finals. We still haven't won enough games to get there yet.
"Our focus is on playing our best footy. Joel's will be about how diligent and how well he does his rehab program."
Cox has also been forced to find a replacement for injured defender Sam Wicks (hamstring), floating veteran Dane Rampe as a possible option.
Former co-captain Rampe, 36, hasn't played since round nine after suffering a calf strain, but made a successful return to the VFL last week.
"It'll be good to have him (Rampe) back in the team," Cox said.
"Just the experience he's had - the way he can communicate behind the ball and set up what we need to do. He's done it for his whole career.
"There's a chance for him to come back and do that. It's not about him doing anything else other than what's required at a certain moment. We'll expect him to do that."
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