Previous boss Paolo Di Canio looked to overhaul the squad when he and director of football Roberto De Fanti oversaw the acquisition of 14 players over the summer.
But, since Di Canio's departure, caretaker Kevin Ball and now Poyet have leaned heavily towards the players who were already at the club before the summer.
However, Poyet insists he has assessed every player and is picking the team he wants.
Asked why so many of the summer signings were not involved, he answered: "I've got an explanation, but unfortunately I can't share it with you. I wasn't here so I don't know what the situation was with the other players and why it was needed."
Sunderland face Southampton in the Capital One Cup on Wednesday night and will be without Lee Cattermole and Andrea Dossena after the pair were sent off against Hull City at the weekend.
Regarding team selection he continued: "It's the manager's prerogative, the decision of the manager.
"I came here and tried to analyse the quality of the players and the squad and, depending on what I think for Sunday, I will pick those players.
"I don't think 'he's been here for five years' so I'll pick him or 'he's been here since the summer' I'll pick him. It's all the same for me.
"The ones who are performing stay on the pitch, the ones who don't are out. I have two players out for three games. There are two positions to grab because of that.
"If the players who come in play then Andrea and Lee have a problem.
"It's not depending on me, it's depending on the players who're coming in. If they don't perform then the others have a chance to come back. For me, it's one team, one group and it doesn't matter where you come from, if you're tall or small, fat or skinny you are the same.
"If I need you then you play. I don't analyse if you were here before the summer or not.
"Then next week in the international break I'll have a proper report on each player and we'll move on from there."
Poeyt admits it is not easy, particularly for the newer players who are no longer involved, adding: "I'm sure it's not easy for them and it's even more difficult for the staff to keep them happy because they've moved with their families and a few are not even making the bench.
"When you move you move for a reason with expectations and we try to manage the best we can which isn't easy.
"It's part of the job that's not easy but not nice, there are players that whatever you tell them they won't accept it because they came for a reason and that's to play."
Meanwhile, Poyet has warned his players not to let discipline become an issue if they want to stay in the team.
Cattermole and Dossena were sent off within minutes of each other in the first half of Saturday's 1-0 Premier League defeat at Hull which left the club still deep in trouble, and they will not be available again until Sunderland travel to Aston Villa on the final day of this month.
"For me, it was a surprise. I need to analyse from the moment I came here, it was all right. I'm not saying it was perfect, but it was not bad," Poyet said of the club's discipline.
"Now so many things happened in this game that I'm trying to take it as a one-off. Of course, we need to talk about it and sort it out - it shouldn't happen again.
"But we are human beings, the players on the pitch, and they are the ones who need to control themselves.
"We can talk and talk and bring in whoever you like, psychologists, psychiatrists or whatever, but then the one on the pitch is the player and the one who makes the tackle or the reaction is the player.
"If they learn, great; if they don't, then they are going to have a problem to play in the team because they are going to be more out than in."
While the cup may not be the Black Cats' main priority this season, the manager is hoping the game can help to forge a level of consistency ahead of Sunday's daunting clash with Manchester City.
He said: "I try not to put it on a different level to anything, not because I want to give it more or less importance because we need to keep improving.
"We need to keep getting better. We need plenty of things, we need to do better for longer periods during the game, not only 45 minutes.
"It's another game, another important test against a very good team, so use it as another step forward. It's quite important.
"I know if you put in the balance would you prefer to win on Sunday... That's too easy.
"I don't know what is going to happen tomorrow, I don't know what is going to happen on Sunday. First things first - let's play tomorrow and try to win."