The Black Cats are bottom of the Premier League after Crystal Palace's win over West Ham on Tuesday, and Poyet's knows his players need to show him what they are capable of in the coming weeks.
"When you are coming close to January, you are thinking what you need to do," Poyet told the Daily Mirror.
"The more the team improves, the fewer changes you will see. There is a limit. I cannot go until December 28 waiting to see positive signs.
"So the next few weeks are important, deciding if we need two new players or five. I have an idea of what I want to do in January, but there is time for that to change.
"But it is not like I am not going to bring anyone in. I will. Depending on the next two or three weeks, it could change the number I make. If we don't keep improving, we need a bigger shake-up. It is a way of saying it depends on the player.
"The next few games, we need consistent improvement. It is not good making progress one game then relaxing and sitting back. Be solid and consistent, and scoring. Can we score? From two yards, take better chances?"
Former club Chelsea visit Wearside on Wednesday and Poyet admits his side need to claim some wins before Christmas.
"Mentally for me it is just better to think about the next game. But, of course, we need to win a few games before Christmas," he said.
"Look, it's true that you look at the table. People who say they don't look at the table, they are probably lying.
"But for us, the aim is to keep getting points. We need to make sure that we win 10 or 11 games, that's the aim - it doesn't matter against who - and then we will see.
"If the rest are better than us, then you need to take it, but we can't do more than just look after ourselves and win football games."
Poyet admits he is very much still a Chelsea fan following his time at Stamford Bridge.
"If I was without a job and living in London, I would be going to watch Chelsea at the weekend. No doubt I would be there," he said.
"I am a fan. I will always love the club."