Sometimes a player leaving Celtic simply makes sense.
Sometimes, though, what happens next makes you look back at the decision rather differently.
Stephen Welsh falls firmly into the second category.
Only a few months ago, Celtic agreed to terminate the final year of the defender’s contract and allowed their academy graduate to join Swansea City on a free transfer.
Now look at him.
Welsh’s career has exploded since Celtic exit
Welsh has gone from being surplus to requirements at Celtic to playing regularly for Swansea City, helping them make an excellent start to their Championship campaign.
Then came something even bigger.
A first senior Scotland call-up was followed by a first senior Scotland cap, with Welsh starting against Slovenia and helping his country keep a clean sheet in a 0-0 draw.
For a player who spent years struggling to establish himself permanently at Celtic, the transformation is striking.
And Welsh himself has effectively explained why.
Speaking after receiving his Scotland call-up, the 26-year-old described the last 18 months as the best football of his career.
There is a lesson in there for Celtic.
Was Celtic ever the problem?
This shouldn’t become revisionist history.
Welsh was given opportunities at Celtic and never established himself as an automatic first-choice centre-back.
But there is a difference between deciding somebody isn’t good enough and asking whether you created the environment for that player to become good enough.
Welsh made 21 appearances during 2020/21 and another 24 the following season.
After that, his opportunities dramatically reduced.
Regular football elsewhere changed everything.
His spell with Motherwell was excellent. Swansea then wanted him, gave him regular Championship football and suddenly Scotland wanted him too.
The player Celtic couldn’t find a regular place for is now an international defender.
Celtic should pay attention
This is why Welsh’s story matters beyond Welsh himself.
Celtic have another academy-developed centre-back in Dane Murray attempting to establish a genuine pathway into the first team.
Developing young footballers isn’t simply about producing them at academy level.
At some point they need minutes.
Welsh’s career since leaving Celtic demonstrates what can happen when a player finally gets them.
Nobody can say with certainty that keeping Welsh would have produced the same performances at Celtic.
Perhaps leaving was precisely what he needed.
But Celtic should still be asking themselves an uncomfortable question.
How did a defender they were prepared to release for nothing become a Championship regular and Scotland international within months?
Whatever the answer, Celtic cannot afford to ignore it.