Ferguson unveiled Dutch defender Alexander Buttner at his Friday news conference, with the former Vitesse player having completed his move to United on Tuesday.
He follows Shinji Kagawa, Robin van Persie and Nick Powell to Old Trafford while Chilean teenager Angelo Henriquez also completed a move to United this week.
But Ferguson insists that there will be no more incoming players despite rumoured interest in Mexico's Hector Herrera.
And time is also running out for Dimitar Berbatov, who is trying to seal a move away following the arrival of Robin van Persie.
Ferguson told reporters: "We definitely won't be buying anyone else, that's for sure. There's no movement I can tell you about. There's only a few days left to the deadline and it will all pass quickly, I imagine."
Van Persie made his debut in United's 1-0 defeat to Everton on Monday night as a late substitute but Ferguson has revealed the Dutchman could start when United face Fulham at Old Trafford on Saturday.
The United boss admitted he would prefer the former Arsenal striker to have more games -- but is ready to give him a start.
He said: "He's had a few days training since Monday. In an ideal world he would be better with two or three games under his belt but it's a home game and there's every chance he could start."
Ferguson also revealed that Buttner will provide the right competition for Patrice Evra, as the Frenchman has been playing too much in recent seasons.
"It gives us that back up as you said we have defensive injuries at the moment," he added.
"Patrice Evra could play centre back, he has done before in the past but it gives us a stronger squad, that's the most important thing."
"Buttner's a straight-forward, attacking, quick full back. He will be a terrific addition to us.
"When you consider Patrice Evra for the last five years has played an average of 48 games a season. It's an incredible statistic and Alex comes now to challenge that position."
Danny Welbeck signed a new-four year deal with United on Wednesday and Ferguson revealed it was a difficult negotiation with the player's agent, as the striker's injury problems coming through the ranks were a concern.
But the United boss was relieved to tie the England international down.
He said: "It wasn't an easy negotiation with his agent. It's always difficult to assess their level at that age.
"Bearing in mind that Danny has had growth problems all the time, therefore he had a lot of minor injuries that sometimes kept him out for periods.
"Last season was exactly that. He had two injuries but he's getting stronger and in two years he will be an outstanding player. We're delighted to get him on a contract."
Ferguson has now called on his side to bounce back following Monday's surprise defeat to Everton but knows that they are facing a difficult challenge against Fulham.
"I went to see Fulham on Saturday, they played very well. The club has grown tremendously since Roy (Hodgson) got them to the Europa League final.
"The place is buzzing, full house every week, good atmosphere, their home record is terrific and they've got a lot of experienced players -- six players over 30.
"It won't be an easy game, we're at home, we have to make an impact quickly after losing Monday night and we expect that."