This season has witnessed a levelling out of results, with the champions suffering more than title rivals Chelsea and Arsenal as clubs outside the Big Four up the ante.
The Reds have lost five matches at the 20-game mark, compared to league leaders Chelsea's three and Arsenal's four.
Rafa Benitez's Liverpool have lost seven league matches and are in seventh position.
The last time United lost five by the same stage of the season was in 2002-03.
They did go on to win the title by putting together a 17-match unbeaten run after back-to-back January defeats against Blackburn and Middlesbrough.
But the trend in upsets looks set to continue and Fergie says Birmingham, who United visit for a tea-time fixture at St Andrews on Saturday weather permitting, are typical of the the unusual development in the top division. "There is an improvement in the league," said Sir Alex. "Look at Birmingham and the fantastic job Alex McLeish has done.
"He brought Barry Ferguson down from Rangers. He brought the centre-half from Cardiff (Roger Johnson) but he has used players who have been there for a long time now.
"What he has done has been fantastic. They are now eighth in the league. They have gone 11 games without defeat in the Premier League.
"The general standard of the league has improved. That is why you are getting so many different results. The vital answer to it is can you keep all your players fit? That is a big ask given the competitive element of the league.
"Teams who are doing well and want to keep doing well need a good nucleus of players to work with. Then you can pick your strongest possible team every week.
"The league has lacked a consistent team that has gone a few wins in a row. It is so tight."
Source: Manchester Evening News