Four years on, the striker is a player who can make a major difference between a team staying up or going down.
Clarke marked his recall with two goals in an impressive victory over promotion-chasing Leicester City.
He was dropped to the bench for the previous five games and, in years gone by, would have been sorely tempted to sulk.
Now, however, Clarke appreciates the value of biting your lip and knuckling down and his patience was rewarded by manager Alan Irvine.
Recalled at the expense of loan signing Luke Varney, Clarke shone and was substituted near the end to a standing ovation.
He looks fitter, oozes confidence and is no longer a pushover for defenders.
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With the Owls locked in a battle for survival, that sort of performance will not only help the cause but also help safeguard his own future.
"As a player, when I was younger, I was a bit immature at times," he said. "A few people let me know about it, too, but I think I have matured as a person since I have been in Sheffield.
"There have been times when it has been difficult for me and I could have just caved in and said 'forget it, I'll just take it easy until the end of the season, or go on loan to a League One or Two team' but that's not what I want to do now. I want to play at the highest level and get my head down and work hard.
"I spoke to the manager last week about what I can do and he now wants me to deliver it on a more consistent basis. It's not about individuals, it is about the team and sticking together.
"A lot of the boys are out of contract, myself included, but we are trying to let our performances do the talking. We will see what happens at the end of the season," he added.
Clarke, who has been on loan four times, won over the Owls supporters after a difficult start to his Hillsborough career and took just six minutes to justify his selection against Leicester.
Latching onto a pass from Tommy Miller, he unleashed a sizzling shot from just inside the area which flew into the roof of net.
An early goal was exactly what Wednesday needed to settle nerves after four defeats in the previous five games.
Irvine had reacted to the 5-0 hammering at Reading by making four changes to his side and all those brought in played well.
Captain Darren Purse organised at the back, Jermaine Johnson posed a threat down the flank and Clarke worked hard in the final third.
Equally admirable was the performance of midfielder Miller – so often injured since his arrival last summer – who slotted in comfortably on the left wing, showed a good eye for a pass, and was aware of his responsibilities in defensive areas.
Leicester, unbeaten in eight, took time to recover from the early setback but Owls goalkeeper Lee Grant needed to produce a brilliant save to stop midfielder Andy King equalising after 26 minutes.
After suffering a gash to the head in a challenge with Marcus Tudgay, Leicester goalkeeper Chris Weale had to be replaced by substitute Conrad Logan.
Weale had played in every minute of every game for Leicester so far this season but his replacement stood up to examination.
Owls defender Tommy Spurr fell heavily just before the break and was taken to hospital with suspected concussion; versatile loan signing Eddie Nolan switched to left-back and showed his qualities.
Wednesday started the second half just as they had done the first – putting Leicester under the cosh.
Logan pushed Johnson's shot around the post and Clarke began to ruffle feathers.
It was a link-up between Johnson and Clarke that brought the crucial second goal.
Johnson could have been a Premier League player if his final ball was more reliable yet there are still enough flashes of quality in his game for the Jamaican to be an asset for the Owls.
His delivery to Clarke was perfect although slack marking aided the job of scoring.
Had Grant not finger-tipped a drive from King over the bar on 67 minutes, the Owls might have come under more pressure.
Clarke's second goal had, to a great extent, extinguished the visitors' hopes of salvaging anything.
Asked how he planned to celebrate, Clarke insisted that he would simply be going to Tesco to find something to eat while watching 'Match of the Day.'
Another sign of maturity? Possibly. However, one of the changes Irvine has made since arriving, is having players in for training on Sundays before a midweek game.
Sheffield Wednesday: Grant; Nolan, Purse, Beevers, Spurr (Simek 45); Miller, O'Connor, Potter, Johnson (Varney 69); Clarke (Soares 83), Tudgay. Unused substitutes: McAllister, Jeffers, O'Donnell, Gray.
Leicester City: Weale (Logan 31); Morrison, Hobbs, Brown, Berner (Howard 69); Wellens; Gallagher (Kermorgant 69) Oakley, King, Dyer; Waghorn. Unused substitutes: Solano, Adams, N'Guessan, Bruce.
Referee: P Gibbs (West Midlands).
Hero: Leon Clarke
The Owls striker grabbed both goals and worked tirelessly for his side. However, all four players who were recalled to the team by manager Alan Irvine justified their selection and contributed to an impressive win in the on-going battle to avoid the drop.
Villain: Phil Gibbs
Mystified both managers with some of his decisions and, in his first season on the national list of referees, appeared to crack under the pressure at Hillsborough. Looked even worse in pink.
Key moment: 6th minute
Clarke's early goal puts Wednesday in the lead and settles the nerves among players and supporters.
Ref watch: Phil Gibbs
Will need to study this performance in detail in order to learn from a string of mistakes. Jeered off the pitch at the end.
Priceless win for the Owls which highlighted the value of having a fully-fit squad again. This win should also revive confidence for the remaining 12 games.
West Bromwich Albion v Sheffield Weds, tomorrow, Championship, 7.45pm.
Quote of the day
I live in Sheffield so (after losing to Reading) I just tried to keep my head down and stayed in the house. I didn't go out shopping or eating.
– Owls striker Leon Clarke on the best way to avoid criticism.
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