It seems amazing that a team capable of opening the season with a 16-match unbeaten run and cruising into the knockout stages of the Champions League by conceding just a single goal can be doubted by so many.

Yet the critics are adamant United are not as good as in years gone by.

Even Monday's Old Trafford victory over Arsenal, that sent the Red Devils two points clear at the top with a game in hand, has not silenced some.

Ferdinand wonders if those dissenting voices belong to those who secretly want United to fail.

Because the 32-year-old defender has no concerns at all about the Red Devils' quality.

"I don't understand it but that is the way it is," he said.

"In the last four seasons we won the title three times. But on each of those occasions we didn't start the following season as favourites.

"That tells you something. People either don't think we are as good as we are, or don't want us to be.

"But within the walls of Manchester United, we know. And we also know what we are capable of.

"We have not had the greatest season yet in terms of consistency but that is what we are aiming for."

In one sense, consistency is exactly what United have had given their enduring ability to avoid defeat.

Yet it is those disappointing draws at Fulham and Everton, plus the loss of a two-goal lead to West Brom, that seem to linger longest in the memory.

Since all those setbacks, though, United have achieved far more notable results - Park Ji-sung's stoppage-time rescue mission against Wolves, an unlikely comeback at Aston Villa when - by Sir Alex Ferguson's own admission - United should have been buried, that seven-goal annihilation of Blackburn and finally Monday's crucial triumph.

None of United's rivals have been able to put together such a consistent run of positive results.

Certainly not Chelsea, who may boast an unbeaten home record against United that extends back to 2002 but have just one Premier League victory to their name in seven outings since the beginning of November.

Ferdinand is not convinced the recent absence of Frank Lampard can entirely account for Chelsea's misfortune, even if he rates his old West Ham team-mate as their best player.

"Frank has been a big loss for them," said Ferdinand.

"I would say Frank is their best player. He gets 20 goals a season from midfield, which is huge.

"Any team that loses that is bound to be affected.

"But Chelsea would say themselves they are not a one-man team.

"Frank missed a few games earlier in the season but no-one was saying anything then because they were winning games.

"When a club loses games people look for excuses. Frank being out is one that has been brought up a lot."

Chelsea's need for victory is clearly more acute than United's.

Even now the champions are trying to claw back two victories. Turn the gap into six points having played a game more and the task would appear to be beyond them.

Not that Ferdinand believes anything too significant can be read into this crazy campaign.

"It would be a blow to them if we got six points in front but they were six or seven clear of us a month ago," said Ferdinand.

"It can all change so quickly if you have a bad run.

"It would be a good boost for us if we could win but it won't define our season."