United's 2-1 home defeat to Man City has left them five points adrift of table-toppers Arsenal who visit Old Trafford for the FA Cup 5th round tie this weekend.
"It was a very bad weekend," Ferdinand told MUTV.
"We've all been thinking about the reasons why it happened and how we want to pull ourselves together and get the result out of our minds.
"The best thing you can do is to come into training and just get focused on winning the next game, and that's what we're doing."