The Red Devils have been frustrated in their pursuit of a new central defender in particular, although Sanchez is hopeful that the midfield options could help him to raise his own level of performance during the upcoming season.
"I would have liked that they had signed many more world-class players. But it's the club's decision," Sanchez told ESPN.
"The truth is that [Fred] impressed me a lot in his first game. It's what the team lacked - someone who plays 'jogo bonito,' as they say in Brazil. And Andreas Pereira too. I think they are two players who have quality and they could help me a lot.
"Today I am more comfortable. I am calm. My teammates have to be focused. I also have to. I depend on them. If they are well, me too. It's [improving] positively, it goes better.
"I think it will be seen now in the games when we play with Paul [Pogba], with Fred with [Romelu] Lukaku and with all the rest who are playing. There we will understand better which is the best way [to get the most out of the team]."
United will get their Premier League campaign underway on Friday night when they host Leicester City at Old Trafford.