The arrival of Leone Nakarawa in 2013 and his departure, to France, this summer were two seismic days in the history of the Warriors.
Nakarawa was a giant in physical stature and a colossus of entertainment and public relations, a player whose world class was obvious and whose box office appeal to young and old was incalculable and irreplaceable.
The rugby show at Scotstoun has lost its ringmaster to the riches of the Top 14. What a gap the great man leaves behind.
Gregor Townsend has to find a way of plugging that gap. Few will doubt him. The Pro12 season begins this weekend and while Leinster are deemed favourites to lift the title, Glasgow are second. They may have lost their crown and their phenomenon in the second row, but there's a formidable group and culture there - and a deeply canny coach.
There is new blood. Well, newish. Corey Flynn, the former All Black hooker, is 35 years old, and Nemia Kenatale, the 39-times capped Fijian scrum-half, is 30. The other notables are Leonardo Sarto, the hulking wing from Italy, Tjiuee Uanivi, the lock from Namibia, Djustice Sears-Duru, the prop from Canada and Jarrod Firth, another prop, from New Zealand.
These are troubling times for the Pro12. Mark Dodson, the chief executive of Scottish Rugby, and Philip Browne, his counterpart in Ireland, have sent up distress flares about the chronic need for change.
More television revenue is needed or the future is bleak. There is talk about creating a franchise in the east coast of America in an attempt to tap into a new and potentially vast market.
For all the Pro12's problems - its lack of money, glamour and crowds in comparison to the rich leagues of England and France - there is one unarguable strength and that is its growing importance to those who compete in it.
For much of its history, the Pro12 was an after-thought to the three giant provinces in Ireland, a training exercise for the stuff that really mattered to them - Europe.
Leinster, Munster and Ulster could compete among the elite back then. These were the days before the English and French went into overdrive with their TV deals. The Pro12 was a warm-up act to facilitate the greater ambition.
Those days are disappearing fast. Whether they're returning anytime soon is doubtful. For the first time since the turn of the millennium, none of the Irish teams made it to the quarter-finals of Europe last season. Ulster were close, Munster and Leinster a mile off. For the pair of them, there was humiliation along the way.
In the age of the super-rich clubs in England and France, the Pro12 is fast becoming their only chance of silverware.
Munster are coming into this with a new coaching team, headed by former Springbok Rassie Erasmus. The two-time European champions are in need of change.
When they get their players fit - critical men such as Peter O'Mahony and Francis Saili are still on the treatment table - and assimilate their new South African lock, Jean Kleyn, then Munster will be decent but you wonder if their squad is deep enough for the long haul.
Ulster have brought in the brilliant Kiwi full-back Charles Piutau and the forceful Springbok back-row Marcell Coetzee who, admittedly, won't be back from injury until early next year. Having made the Pro12 semi-finals last year, Ulster will be a short price to do the same again.
The champions Connacht? They've lost key men - Robbie Henshaw, AJ MacGinty and, most wounding of all, the rock of their pack, Aly Muldowney.
Things will be different for the champions. They have several players who were unwanted by Ireland a year ago but who will now be taken from them by Joe Schmidt at various points of the season.
Townsend, and others, have had their squad affected significantly by Test rugby for some time. Connacht coach Pat Lam is about to experience that.
Leinster 's strong title credentials are built on a huge squad with a battalion of young players on the verge of a breakthrough.
Luke Fitzgerald and Eoin Reddan have retired and their loss will be felt. Ben Te'o, one of their most important players last season, has gone to England. Ian Madigan has gone to France. They have Henshaw, but he is out for six weeks. There's huge pressure on Leo Cullen, the coach. He needs to make something happen this season.
Scarlets have strengthened, arguably, more than anybody else.
Jonathan Davies has come in from Clermont, Rhys Patchell arrives from Cardiff Blues, Werner Kruger - acquired from the Bulls - looks an excellent acquisition in the front row and Johnny McNicholl, the former Crusaders wing/full-back, could be the signing of the summer.
What of Edinburgh? They have a group capable of a top-four placing but you could not hang your hat on them. With a ninth-place finish last season, there are questions about inconsistency and underachievement. Until there are sustained signs of a shift in that respect, then they cannot be trusted to push for the top positions.
We always expect Glasgow to deliver in the Pro12 because they have been doing it for so long. The hope for them is that Townsend's impending exit next June, to replace Vern Cotter as Scotland coach, is not a distraction. It shouldn't be. Good players do not look for excuses - and Glasgow still have an awful lot of good players.
There are many teams in the mix for the title: Leinster, Ulster, Munster, Scarlet, Connacht. Edinburgh as well, perhaps, if they can find their form. The side they'll all be looking out for warily, though, is Glasgow. The Warriors may have lost their title but they haven't lost their reputation.
Of all the business done by Glasgow Warriors in the last three years - more than 40 players in and more than 50 players out - there are two transactions that stand out above all others, and both relate to the same man.