Jurgen Klopp said he cannot keep all of his Liverpool squad happy, but he does not believe that will be a problem for the Premier League leaders.
Liverpool moved back to the top of the pile on Sunday, with Xherdan Shaqiri's double securing a 3-1 win over Manchester United.
Alisson's error had allowed Jesse Lingard to square things up after Sadio Mane's opener, but Shaqiri's introduction in the 70th minute paved the way for Liverpool to make their dominance count.
And although Klopp was delighted with Shaqiri's impact from the bench, he said that players must prove their worth if they are to keep a place in his XI.
"I cannot keep players happy," Klopp told a news conference.
"You are happy or not happy, you understand it or you don't understand it.
"A big squad isn't there to make each member of the squad happy. I think the boys understand it. That's how it is.
"So rotation, whatever it is, in that intense period there are two opportunities. You play all the time until you are injured, or when we have to manage games.
"These are the only two possibilities. This is the Premier League. You cannot manage games.
"That means we have to make changes. I'd prefer to make these changes before the boys are injured. Then there are specific jobs to do against specific opponents."
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Defender Nathaniel Clyne made his first league appearance of the season against Jose Mourinho's side, and Klopp used the full-back as an example of the quality required from his squad players.
"The best example is Nathaniel Clyne," Klopp said.
"Since I have been here, he has played 100 or so games, then he got a bad injury and was out.
"Trent [Alexander-Arnold] emerged, then Joe [Gomez] got fit, and the situation changed.
"You can train at the highest level, but you have to wait. Is that nice? No. Is it the job? Yes. That's how it is."
