Sir Alex Ferguson believed that most football teams operate in four year cycles. There were only a number of team talks players could react positively to, their best-before date with one philosophy winding down with each match.
The Manchester United legend was also blessed with a stack of players any Football Manager addict would be happy of picking up on youth intake day - the Class of '92 were stalwarts at the club, while the likes of Roy Keane, Wayne Rooney, Peter Schmeichel, and many others enjoyed long, successful spells at Old Trafford. These are the outliers, the elite talent that can find it within themselves to get up and go again for longer than the average footballer.
Mauricio Pochettino's problem at Tottenham is that the cycle is ending, and he does not have enough top talent to keep a flickering light burning for much longer.
Spurs are undoubtedly one of Europe's top sides, yet have no silverware under the Argentine to show for it. Their peak came between late 2015 and the end of the 2018/19 season. In that time, they achieved their highest ever Premier League finish and points total, gaining more points over the 2015/16 and 2016/17 seasons than any other side. They've also qualified for the Champions League for a club-record four seasons in a row, playing in their first final back in June.
Their starting point in the modern football era compared to their domestic rivals and net spend in that time make these accomplishments in their own right, but Pochettino has stressed the importance of changing the culture at the club from nearly-men to winners. However, that ship may have sailed.
Pochettino's first grumblings about this issue came at the end of the 2017/18 season, saying the club needed to "be brave and take risks" in order to bridge the gap. That summer, there weren't any senior incomings or outgoings.
The rebuild that was needed at Spurs did not occur, and their league form suffered for it, losing 13 Premier League games last season. A stale squad that lacked the desire and, more importantly, the quality to challenge the top clubs meant a miracle was needed to win major honours.
Tottenham's run in the Champions League was just that - a miracle. Every player in their European campaign squeezed every last ounce of energy into ensuring they reached the final, playing in a more pragmatic manner than Pochettino would probably prefer.
Spurs' window to try their luck at the Champions League realistically came the season before, topping a group of death featuring Real Madrid and Borussia Dortmund, before cruelly falling to Juventus in the round of 16 despite being the better side. This was, though, a Tottenham team more fitting of Pochettino's vision, and if they had knocked out Juve, the world was at their feet.
The summer of 2018 was the time to rebuild. It was a time to shift the deadwood and keep the team fresh physically and mentally - particularly after a taxing World Cup resulted in fitness issues over the entirety of the following season for several key players. Spurs stalled and went in reverse when the opportunity to move forward was staring them in the face.
While Tanguy Ndombele, Giovani Lo Celso, Ryan Sessegnon and Jack Clarke are all great signings, it might be too late for the team in this iteration to take the next step. Christian Eriksen, Toby Alderweireld and Jan Vertonghen all have contracts up at the end of the season, and Pochettino would rather not have this uncertainty looming over Spurs.
Beyond them, there are several players whose quality has declined in the last couple of years; Eric Dier and Victor Wanyama's fitness issues mean they are not valid squad options, Danny Rose was close to joining Watford on deadline day, and there is a general lack of depth. The majority of the team have been at Tottenham for four years or more. The cycle has ended.
With Zinedine Zidane on the brink at Real Madrid, you imagine it would be hard for Pochettino to turn them down again, particularly with the rebuild challenge at Spurs already a year behind schedule.