Former Celtic striker, Joe Miller, believes the 20-year-old's departure to Standard Liege in a five-year deal which will be worth £1.2million is magnificent business for the club, and for the player.
But it could all have been so different.
The goal Watt scored against Barcelona in 2012 should have provided the launch pad to a long career as a Hoops hero.
Instead, it has marked the beginning of his decline at Parkhead as he failed to kick on from his magic moment against Messi and Co.
Now, like many Miller has watched before him, Watt has got to start all over again in an attempt to avoid becoming a man who failed to realise his potential.
"Having watched how it has gone for Tony since that night against Barcelona, I felt he had to leave because it just wasn't going to happen for him here," said the man who won the title and the Scottish Cup twice with the Hoops.
"He was always a fringe player. Even when they played Barcelona that night, he was on the bench.
"Neill Lennon had a lot of players missing through injury and suspension, so he sent them out to play very defensively, which they did as a unit very well.
"Then Lenny went for it late in the game, sending Tony on.
"It worked out magnificently with him scoring what turned out to be the winning goal.
"Tony will forever be remembered for that. But, in reality, he didn't do much else.
"It's a classic case of a young lad having pace, strength and the ability to score.
"But how many times have we seen young lads think they are the next big thing - lads like Garry O'Connor and Derek Riordan - only for the penny to drop too late that they need to have the full package.
"To make all you should of your career, that means the right attitude as well as the right skill set."
Lennon got frustrated at the missing piece in the Watt jigsaw, hence the loaning to Lierse in Belgium last season.
The hope was that, removed from Lennoxtown and Parkhead, the youngster would realise just what he had here, and the maturing process would be accelerated.
Removing Watt from his social scene was another important element in the plan.
But the tactic failed, and Ronny Deila has agreed it would be best for all concerned if they parted company.
Miller warns Watt must heed this wake-up call, and said: "I hope he makes the most of this second chance.
"He needs to set himself a plan to make a success of his time in Belgium and do well enough to get back into the Scotland squad.
"I also hope Ronny Deila gets the money raised to bring in more players as he attempts to make the changes he wants to see in the team.
"I watched their game in Iceland and was at Murryafield for the return leg last week.
"To be honest, I don't really see much difference from the way they played before. But it will take time."