The United boss has confirmed the deal to sign Evra from Monaco is done and providing the 24-year-old French international passes a medical on Monday, will link up with his new team-mates in time to face Mark Hughes' men at Ewood Park.
Ferguson has been monitoring Evra's progress ever since Gabriel Heinze ruptured his cruciate ligaments in September and although Inter Milan were also interested, Red Devils chief executive David Gill flew in to Monaco on Thursday to agree a fee which is estimated to be around £5million.
"I have been looking at Patrice for quite a while," confirmed Ferguson.
"He has improved each year since he has been with Monaco. He is very quick, naturally left-footed and a good footballer.
"We cut the squad numbers quite dramatically at the start of the season and then with Gabriel Heinze being out for a year and Quinton Fortune missing as well, we needed to bring in a left-sided player.
"Patrice has only had a couple of weeks off, so he is ready to play almost immediately and the registration deadline for the Blackburn game is not until Tuesday."
Providing the deal goes through, it will take Ferguson's spending to £12million following the earlier purchase of Nemanja Vidic.
The United boss skirted around the subject of any further new arrivals Thomas Gravesen has been mentioned but denied flatly the reinforcement of his defence would signal the end of Mikael Silvestre's seven-year Old Trafford career.
"It doesn't mean that at all," said Ferguson when asked if Silvestre would now be on his way.
"We are trying to bring players in because we didn't have the squad to cover all eventualities."
Although Evra can also be used in midfield, his initial job will be to help shore up United's defence, with Vidic being given the same job, almost certainly alongside Rio Ferdinand at centre-half, once he gets his fitness up to the required levels.
The 24-year-old Serbian defender has not played a competitive game since the Russian season came to an end on November 22 and has been limited to endurance work only on his first two days at United's Carrington training complex.
Ferguson has already stated Vidic will not be involved in tomorrow's FA Cup tie at Burton, nor the Blackburn game, so a reserve team outing against Leeds next Thursday seems likely if he is to stand any chance of facing Manchester City on January 14.