The two young forwards are in a battle to fill the void left by their Kiwi team-mate during the forthcoming FIFA World Cup qualifying playoffs
Barbarouses will miss Victory's next two matches, away to Sydney and Western Sydney, due to his international commitments with New Zealand's All Whites.
Pain appears the front-runner for the vacant attacking berth after starting twice and making two substitute appearances in four A-League matches so far this season, Gui Finkler is still feeling his way back from a long-term knee injury, while Nabbout has come off the bench just once in 2013-14.
But the latter player has 'Big Blue' history counting in his favour. With the Victory trailing 2-0 and just 22 minutes remaining in the same fixture at Allianz Stadium 12 months ago, he came on and netted twice in a memorable comeback 3-2 win for the visitors.
When asked on Friday if Pain was a certainty to come into the team, Muscat said: "We've got a couple of (other) options and ideas as well."
"Andrew Nabbout, he likes going to Sydney ... so he'll be in contention also. (The) final decision will be made (later), but we've trained throughout the week with both."
Even if Pain gets the nod to start in the Harbour City, the Victory coach knows he has the option of attempting to coax another remarkable cameo from last season's super-sub.
"Yeah well, if he (Nabbout) tells me he's going to score two when he comes on I'll certainly keep it in mind," Muscat said.
"But he's been waiting patiently and so has Connor Pain. An opportunity has arisen for one of them and it's now up to them to take it."
Victory lost Mitch Nichols to injury early in their 3-2 win over Wellington Phoenix on Monday, but the former Brisbane Roar man has made a swift recovery and is expected to keep his place in the first XI this weekend.
"He was a little bit sore, we had to look after him at the start of the week but he's trained the last two days fully," Muscat said.
"He's ok, no problems."
Sydney meanwhile are out of form and have failed to score in their last three matches, prompting suggestions that it is Victory, despite being the away team, who are obliged to go out and attack their opponents on Saturday.
Stopping short of agreeing with those claims, Muscat said the priority for his players was to perform consistently throughout the game, having impressed early on against the Phoenix, before surrendering the initiative in the second half.
"From our perspective, the onus is on us to play our brand of football," he said.
"Last week that was the disappointing thing. For ... the first half hour we did do so. And we've got to maintain that for longer periods. It didn't look like Melbourne Victory in the second half."