QPR have one point from their opening three Championship games this season and were beaten 7-1 by Coventry City on Saturday.
“I had a few options to go abroad, but it was one of those where if I was going to stay in the Championship, it was only going to be one club and I’m just glad to get it done,” Hayden told the Hoops’ website, external.
Norrington-Davies has made 66 appearances for Sheffield United, and played 14 times in the Championship for the Blades last season.
“I’d like to say I’m on the front foot, aggressive in nature, be that defensively or attacking,” he said, external.
“So now I’m looking forward to getting out there and showing the fans what I can do.”
Saito told the club website, external: “I am so happy because I love QPR people. I am looking forward to playing. I want to make goals and assists.
“When I played, when I received the ball, the fans sang my name. I love them. I’m really looking forward to wearing the shirt and seeing the fans.”