"We have bought young players for the future.
"I remember when I came to England, I needed a couple of months to get used to the league."
Vidic, 25, knows the size of the task facing United as they bid to regain the title and go for Champions League glory but believes the new signings have made the Old Trafford squad even better.
"We have bought more players and I think the team is stronger than last season," he said. "We have also had one more season together.
"We need to improve everywhere. If you want to win the league and go to the final of the Champions League you need to improve everybody and that includes me.
"We need to take one step more to be better this season. If we stay the same as last season that is not good."
He added: "Last season was my first full season and I learnt a lot.
"Now I know where I need to improve, where my weaknesses are and my strengths. All the time players can improve and you need to work."