At the end of May 2008 the young Motherwell striker was rewarded with a Scotland debut after netting 13 times for the Steelmen during the previous season.
He seized the chance given to him by George Burley with both hands, coming off the bench to score Scotland's only goal in a 3-1 defeat to the Czech Republic in Prague.
Clarkson's future seemed filled with promise.
But that was to be one of only two appearances for his country. The second, again as a substitute, came against Argentina at Hampden.
Clarkson, now 26, left Fir Park for npower Championship side Bristol City the following summer and since then his career has taken a turn as turbulent as that flight home from Prague.
After a frustrating first two seasons in which he started just 29 games, Clarkson was sent out on loan to League One Brentford last September.
He then suffered a broken ankle on his return to Ashton Gate in a freak training ground accident in January.
Couple that with the arrival of new manager McInnes at City last October, the Scot found himself released to make way for fresh blood at the end of the season.
Now taking some time out in Dubai before the rigours of hunting for a new club begin, that night in Prague is these days nothing more than a distant holiday romance.
He said: "Was it four years ago? I hadn't even thought about it.
"Playing for Scotland was a great high in my career and came at the right time. I scored on my debut as well. Looking back on it, it was fantastic."
When he returns from Dubai, Clarkson will begin in earnest the search for a new club, with preparations already under way.
He said: "I'm still going through my rehab at Bristol, but in terms of training my ankle now appears to be fine.
"I'm at full fitness now. Before I came away on holiday I managed to get training done and that's me raring to go. Bristol are helping me out until I find somewhere else.
"I enjoyed my time there, but that's football and I'm looking at getting something sorted as soon as I can."
It is the norm in Scotland these days for the cream of the emerging talent in the SPL to harbour loftier aspirations.
A move to England, even to its second – or sometimes third tier – is generally seen as a step up.
However, the English game is not always the promised land it is portrayed to be. After being a regular in claret and amber, Clarkson's lack of game time down south saw his international career stall.
But he insists he has never doubted his decision to take his chance at City.
"I've got no regrets at all," he said. "Obviously I was more in and out of the team at Bristol compared to my time at Motherwell where I played every week.
"I wanted to play regularly but it never happened.
"But I was at Motherwell for nearly 10 years and I felt the time was right to leave. Bristol are a big team and it was a massive opportunity for me. It was too good to turn down."
HE ADDED: "I loved being at Fir Park and it made me the player I am. But when the offer of something new presented itself I decided it was the right option for me."
A month on from being released, Clarkson stands again at a career crossroads. When he returns to more dreich climes in a week's time, he will continue to prepare for the challenges of next season, wherever they may lie.
"I'm just wanting to see what's out there," said the forward, who hasn't ruled out a possible return to the SPL. "I loved my time at Bristol, and being honest I would have loved to have stayed.
"It was unfortunate that the gaffer came in and I was out of contract. It gave him a chance to bring in the players he wants so he can put his own stamp on the team.
"I've started looking out for clubs that are on the hunt for players and I'm keeping all my options open.
"If any clubs approach me then I'll take it from there. I'm looking forward to going in a new direction."