Jose Mourinho believes the Premier League landscape has changed to such an extent that Manchester United are no longer able to entice their rivals with big-money offers for players.
United were once the financial powerhouses in the English top-flight but the proliferation of billionaire owners and the lucrative broadcast deals means other clubs no longer feel obliged to sell their prize assets.
Mourinho pointed to the example of United paying large sums to Tottenham for Michael Carrick and Dimitar Berbatov and asserted that a similar swoop for Harry Kane or Dele Alli, for example, would be nigh-on impossible.
The Portuguese therefore accepts that any additions to his squad may have to be below the elite level - although he expects minimal movement at United in the January transfer window.
He said: "It's more difficult to buy players of a high, high, high level. The clubs are more powerful. The clubs don't want to sell, and to sell is to go to absolutely incredible levels.
"Before the smaller clubs were almost begging the big clubs, 'Get my best players. I need to sell. Please, you are powerful. Buy my best player'. At this moment, they don't want to sell.
"A few years ago, who was Tottenham's best player? Michael Carrick. And a few years later, who was the best player? Berbatov. Can we go there now and bring Harry Kane? Dele Alli, [Christian] Eriksen, Son [Heung-min]? Can we go there and bring those players here? No.
"The transfer market is very difficult unless the clubs want to go to what I call crazy numbers.
"You have no chance in the market unless you go to crazy numbers, or instead you go to what you call the second level players and still have crazy numbers, but that second level is the level people say, and I agree, that's not what Manchester United is.
"Honestly, I don't think we are going to sign [anyone in January]. If we do, I would say one player. I don't see us going more than that."
United visit Southampton at teatime on Saturday as they head into a month where Mourinho is eyeing a concerted push up the table as they look to close the gap on the top four.
He anticipates being without Alexis Sanchez for the hectic festive schedule, with the Chilean forward set for around six weeks on the sidelines after injuring his hamstring in training on Thursday.
Sanchez has endured a disappointing few months since leaving Arsenal for United in January and was left out of the squad altogether for the midweek Champions League win over Young Boys.
Mourinho rejected speculation of a falling out with Sanchez, and empathised with the 29-year-old's fortunes, as he expressed his exasperation that other managers are not similarly scrutinised for how they treat their big names.
He added: "When we speak about Alexis, I think you should ask why every time a player is not playing in Manchester United, there is always a rumour. There is always a problem. It's only here.
"In Chelsea when Willian doesn't play there is no problem with Willian and [Maurizio] Sarri. In Man City, when Gabriel Jesus is not playing for weeks, there is never a problem. It is just a normal decision.
"Here is the only club where every day the manager has problems with the players. You make me feel very, very special because I am the one who is different from everybody else.
"But speaking about Alexis - a frustrating season. It's a season where he is not playing a lot, where he had small injuries, where he now has a big injury.
"I don't like and don't believe in the word curse but I have to admit it was probably a very unlucky six months, and we expect the new year brings better things for him."