He'd booted four goals to that point and was clearly the most dangerous key forward on the ground.
Patrick Dangerfield was leading at him, but with his coaches' advice ringing in his ears to back himself when in range, Johnston loaded up to ice the game.
And missed everything.
Johnston could have passed to Dangerfield - he readily admits it was an option – but he backed himself to convert, as his instinct and coaching told him to do.
Despite partly blaming himself for the four-point loss, Johnston told AFL.com.au that if he could could rewind the clock, he would have had another shot.
"If I had kicked that goal it would have been the icing on the cake and put us nearly three goals up, instead they took it straight down and they got that bloody lucky bounce.
"If I had taken my chance it could have been a different outcome.
"I would kick that nine out of 10 times and this time was that one that didn't come off.
"I could have passed it to 'Danger', but all week I've been told to back myself inside 50 and my kicking's my best attribute.
"It happened pretty quickly and I went for it, unfortunately for us it just didn't go through."
His coach Brenton Sanderson didn't blame him for taking the shot, claiming post-match that the forward kicked the same goal at training "every week".
Johnston is blessed with incredible natural talent.
At 193cm and 91kg he's tall, strong and is an astounding set shot for goal; so good that triple Magarey Medallist Barrie Robran rates him the best he's seen.
Praise doesn't come higher.
While prodigious junior talent saw Johnston drafted by the Sydney Swans with pick no. 12 at the 2008 NAB AFL Draft, injuries have limited him to just four games.
Twice in his AFL career he has suffered significant injuries as his senior side's emergency, the most recent a knee injury sustained a week after Taylor Walker tore his ACL.
"If I'm in the team I can't be the emergency, which is good because that's where the curse seems to be," he joked.
"My first year I missed the whole season after getting two best on grounds in the reserves, second year I was emergency and kicked six and then tore my hip, then in my third season I did my ankle three times and missed 14 games.
"This year I was first emergency then did my knee – it was frustrating."
Sunday was his first game for the Crows since round 20 last season.
That day against Fremantle was one to forget as he struggled with the speed of the game before being subbed out of the contest goalless.
He's since had to demand selection with consistent performances in the SANFL.
As he posted career-high numbers almost across the board against the Power on Sunday, you sensed a weight lift from his shoulders.
His 17 possessions, seven marks and four majors might not have won his side the game, but it was some return.
"I've put on a few kilos since and I've matured as a person, which has helped me," he said.
"I've always believed I could do it, it's just getting that opportunity and taking advantage of it when it comes.
"I haven't taken my opportunities that well in the past, but today was helpful for the future and hopefully I can get another game."
Harry Thring is a reporter for AFL Media. Follow him on Twitter: @AFL_Harry.
