World No.56 Panama stunned the Matildas 1-0 in Bunbury on Saturday and threatened another boilover on Tuesday night when an Ericka Arauz wonder strike gave the visitors a 1-0 lead in the 34th minute.
Veteran striker Michelle Heyman struck in the 54th and 65th minutes to give the Matildas a 2-1 lead, but the 10,659 crowd were left stunned when Panama's Lineth Cedeno scored in the 83rd minute to level the scores.
Enter Grant.
The 23-year-old Tottenham fullback had huffed and puffed all night long and received her due reward in the 91st minute when she wrestled to get in front of her opponent at the far post so she could knock in Courtney Nevin's cross.
Although the win was a good way to end the Matildas' four-match stint in WA under new coach Joe Montemurro, there's still plenty of work to do.
Australia only have two more international windows to prepare ahead of the 2026 Asian Cup, which kicks off in Perth on March 1.
Montemurro made eight changes to his starting line-up for Tuesday night's game, inserting players including Grant, Heyman, Clare Hunt, Remy Siemsen and Emily van Egmond into the XI.
Australia enjoyed 69 per cent possession in the first half but the focus of keeping the ball as much as possible rather than going long when under pressure brought about their undoing at times.
The most costly moment came in the 34th minute when Jessika Nash passed sideways while under pressure with Panama players lurking.
Arauz ensured the ball didn't make it to Emily Van Egmond, bouncing off her opponent and unleashing a 24-yard strike that curled into the net and sent the Panama players into a frenzy.
The Matildas had just two shots on target in the first half.
Their best chance arrived in the 24th minute when Hayley Raso embarked on a long run before getting off a shot while falling to the turf.
The ball bounced off the inside of the far post and rolled tantalisingly across the face of goal before being momentarily cleared, with Remy Siemsem's follow-up shot well saved by the goalkeeper.
Australia levelled in the 54th minute when an inch-perfect cross from Raso found a running Heyman, who had an easy tap-in from point-blank range.
It was another Raso cross that set up Heyman for her second, with the 37-year-old heading home to send the crowd into raptures.
But the Matildas' frail defence was left wanting in the 83rd minute when a turnover allowed Cedeno to cruise into the box and fire past goalkeeper Chloe Lincoln.
Grant ensured the Matildas had the last laugh, but the win was far from convincing.
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