It's already beginning to happen.
When Jose Mourinho walked through the doors of Tottenham back in November it was always going to be interesting to see how he handled working with Daniel Levy.
In many senses, the latter has held Spurs back in the transfer market.
In the summer of 2018, he failed to sign a single player for the north London outfit. He also rarely provided Mauricio Pochettino with too many funds.
That was never going to suit Mourinho, a man who was used to significant war chests at Chelsea, Real Madrid and Manchester United.
We got our first glimpse of a working relationship between Mourinho and Levy in January when the duo combined to sign former PSV winger Steven Bergwijn.
That was an inspired piece of business and already, he's looking like a smart addition, scoring against both Manchester clubs.
Though, ahead of the summer window, the pair are beginning to clash. This can't be good news for Spurs.
Tottenham had been interested in signing Thomas Meunier, available on a free transfer following the conclusion of his contract at the end of June.
Departing PSG, the defender has now walked through the doors of Borussia Dortmund, but it could have been a very different story.
L'Equipe (via Sport Witness) claimed this week that Mourinho and Levy had differing opinions over signing him.
The former apparently phoned Meunier to discuss a deal and he wasn't against signing.
However, it turns out Levy was against the deal, swooping in and denying the Spurs head coach the chance to sign him.
Sharing different desires, it clearly isn't the best of starts to the summer window.
GIVEMESPORT'S Matt Dawson says...
When Mourinho was signed by Spurs to be their manager, it raised eyebrows not only in England but throughout the footballing world.
For one of the first times in his career, the former Porto boss was joining a club without a reputation for spending money left, right and centre.
Things got off to a bright start in January with the addition of Bergwijn but now proceedings have seemingly taken a turn for the worse.
The strangest part about this story, though, is that it isn't money Levy and Mourinho are arguing over.
In fact, Meunier would have been a free transfer.
It's a worrying sign and doesn't bode well for when Mourinho actually wants to pay a transfer fee for a player.
This is only one difference in opinion, but they'll need to get themselves aligned once the window does finally open.