Agar, who joined the 13-man squad that regained the Border-Gavaskar Trophy following a draw in the Boxing Day Test in Melbourne, is keeping his fingers crossed for his Test return after nearly one-and-a-half years.
"Nothing's guaranteed. That's what I'm saying in my head," Agar, who played his second and last Test in July 2013 in England, was quoted as saying on Cricket Australia website.
The 21-year-old is making his presence felt for domestic side Perth Scorchers in the Big Bash T20 tournament and did pick up the key wicket of Jacques Kallis in Thursday's match against Sydney Thunder.
On the other hand India, who will be playing for pride after trailing 0-2 in the four-match series, may also be looking to include rookie left-arm spinner Akshar Patel to field a two-man spin attack alongwith Ravichandran Ashwin at SCG.
The Test will also see new Indian Test captain Virat Kohli lead the team after Mahendra Singh Dhoni's surprising retirement from the longest format post the Melbourne game.