Franjic suffered a hip injury late in Australia’s 2-0 semi-final win over UAE on Tuesday but played out the match due to the fact Ange Postecoglou had already made his three substitutions.
The defender switched to the wing in the latter stages and Sainsbury is ready to fill in at the back at the weekend if Franjic is ruled out.
"I've played there a few times for [former club Central Coast] Mariners and once in pre-season for [PEC] Zwolle," Sainsbury told reporters.
"It doesn't bother me, I'll just have to adjust and do what the coaches tell me. You can put me in goal if you want to, I'm not fussed. I'll go out there and do the job I'm told."
Franjic is likely to learn the full extent of the injury on Thursday, with Postecoglou prepared to give the defender as much time as possible to prove his fitness.
The Australia boss would likely look to Sainsbury or Mark Milligan to slot in at right-back, with the former having opened his international account in Tuesday's victory.
"To be honest I was trying to stay as calm as I could," Sainsbury added.
"My first goal with the Mariners I got a little bit too excited and five minutes later I started cramping. I just remember trying to stay calm and focus on the game.
"It’s about time [I scored]. We've been working on [set-pieces] at training and I've been getting my head on a few but to get it in a game and in such an important match is a pretty good feeling."
