Bolton told The World Game if that happened, it wouldn't be a reflection on Andrew Redmayne's form since he got back into the side, which has been good, but more an indication of what Popovic thought was the best side he could put out to win this particular game.
Redmayne began the season in goal for Western Sydney and Reddy was signed after splitting with Central Coast Mariners mid-season.
Reddy began his Wanderers stint on the bench as Redmayne continued in the starting side.
After Western Sydney lost 5-2 at home to Wellington Phoenix in round 19, Popovic dropped Redmayne and promoted Reddy, who played six straight games before being dropped for Redmayne after the 2-0 loss to Melbourne Victory in round 25.
One of the goals conceded in that game went under Reddy's diving arm and the general consensus was that he should have been able to make the save.
Redmayne played in the last two rounds of the regular season, which resulted in wins over Central Coast (4-1) and Wellington (2-0).
The Wanderers then had the first weekend of the finals series off - as one of the top two teams.
Asked if he was surprised when Popovic went from Reddy back to Redmayne, Bolton, who played a season with central defender Popovic at Sydney FC in 2007-2008, replied: "No. If any coach is willing to make a call that no-one really expects, it's 'Popa', so I'm never surprised with Popa's changes.
"Whenever he throws a young guy into the team or he leaves (Romeo) Castelen on the bench sometimes, it's no real surprise.
"We don't know what goes on internally, so it's hard to comment on changes that are made, but, to me, Popa is someone who looks at each game in isolation and picks a team he thinks will get the job done for that game.
"Form sometimes goes out the window with that approach, so it's no surprise to me that he makes changes that will surprise others. I think that change, Reddy out and Redmayne back in, surprised a lot of people because they don't know Popa.
"It may not have necessarily been all about the form Reddy was in on the day. He made a mistake with the goal that went under his arm and he should have stopped it, no doubt about that, but maybe that was on the back of a poor week at training or something, we don't know.
"Popa backs his own judgement based on what he sees, and from what I've seen he's got good foresight as far as making changes that turn out to have a positive effect is concerned. He doesn't wait until after the fact to make changes, he anticipates that it's time for a change."
When goals suddenly dried up for Western Sydney late in the regular season, Popovic swiftly elevated "super-sub" Brendon Santalab to the starting side.
That decision was right as the Wanderers then scored six goals in the last two rounds and "Santa" provided four of them.
Bolton agreed Redmayne had gone well since being reinstated, but at the same time he didn't think that was a guarantee he would be in the starting side again on Sunday.
"Redmayne has looked solid, but the thing is, I wouldn't be surprised if Popa made a goalkeeping change again, if he went back to Reddy for this game," Bolton said.
"I wouldn't be surprised at all, even though 'Redders' (Redmayne) has come in and had two solid games.
"Reddy, for me, is more proven in big games, so if Popa went with Reddy for this game, a finals match, that wouldn't surprise me. That's the type of coach Popa is.
"It's a big game in isolation, there's a lot at stake, so it's about who's the best player suited for this scenario, not necessarily the most in-form person, but the best person for this scenario and that's the way it goes.
"Redders hasn't had form in finals, he hasn't had form in big games except for some derbies, so this is a whole different scenario now.
"We're looking at knockout games and if you look at the history of the two 'keepers, Reddy is probably more proven in these type of games.
"That's why I think it's wide open, the position, going into this match."