The 27-year-old centre back has joined the Socceroos' camp in Sarasota, Florida ahead of the June 11 to July 19 World Cup, hoping to stay fit and recapture the form that made him a standout in Australia's run to the last 16 at Qatar 2022.
Some 17 months on from an Achilles injury that was followed by knee problems, Souttar finally returned to action for English club Leicester last month, scoring a goal and playing a full 90 minutes.
"Obviously you are going to go through your ups and downs with your injury, with getting back," Souttar said from Florida.
"There were times I was back training and having a little niggle then having to get another surgery so it’s just that stopping and starting again, the unknown -- are you going to be back in time, are you going to be fit?
"We’ve still got a lot of work to do to get into the final squad because the group’s done really well.
"There is a lot of hard work to go and I’ve just to prove over the next four weeks what I’m capable of doing."
Four years ago, Scotland-born Souttar was also scrambling for fitness in the lead-up to Qatar after suffering an ACL injury.
He ended up playing a key role in Graham Arnold's Australian squad, putting in a couple of colossal defensive performances against Tunisia and Denmark to secure clean sheets and help the Socceroos reach the knockout phase.
Souttar will hope to have a similar impact as Tony Popovic's team look to advance from a group featuring Turkey, Paraguay and the co-hosting United States.
In Souttar's long absence from the national setup, Popovic has relied heavily on Alessandro Circati and Cameron Burgess in central defence while keeping the door open for Souttar.
He will need to battle players like Milos Degenek, Jason Geria and Kye Rowles for a place in Popovic's final 26-man squad.
"If you look at every single position across the squad you’ve got three or four guys challenging," said Souttar.
"It’s just going to keep the standards high like it always has been here. No one is guaranteed a spot."