Sir Alex Ferguson has singled out Barcelona as the main threat to their UEFA Champions League crown.
Both sides were kept apart in the draw for the quarter-finals and semi-finals and should the two meet this year it will be in the final in Rome.
Despite his side's 4-1 demolition at the hands of Liverpool coming three days after the Reds hammered Real Madrid 4-0 the Scot is insistent that the Catalans are the most in-form team going into the last eight.
United face Porto in their quarter-final tie with the winner facing either Arsenal or Villarreal, while Barca tackle Bayern Munich with the victors playing Liverpool or Chelsea in the last four.
"Barcelona are the form team, they have been terrific this season and everyone is taking notice of them," Ferguson said.
"Their first-half performance against Lyon in the second leg of the first knock-out round (which they won 5-2 at the Nou Camp) was absolutely brilliant, they were four up in no time.
"They can be a threat to anybody and are quite rightly one of the favourites."
Despite Liverpool, Arsenal and Chelsea joining the Red Devils in the quarter- finals Ferguson is adamant that Pep Guardiola's side are more dangerous than the English trio.
"Last season we had three (English teams) in the semi-finals and two in the final," he added.
"The previous year there were three in the semis and Liverpool made it to the final.
"But we have to recognise that our threats don't just come from England, the big one will come from Barcelona."
Despite scoring an astonishing 84 goals from 28 league games, 18 more than closest rivals Real from the same amount of games, the 67-year-old believes that it is their improved defensive record which has caught the eye this year.
Ferguson goes on to highlight that Guardiola has made Barca a better team defensively compared to their all out attack attitude under his predecessor Frank Rijkaard.
"I'm not sure they have improved a lot from when we played them last season but they have a better defensive record since Guardiola took over as coach last year," he enthused.
"There has maybe been a bit more concentration on defending than there had been in previous times.
"That's not a criticism of Frank Rijkaard, I just think Guardiola has brought in the awareness that defending is just as important as attacking.
"Gerard Pique, for instance, left us to go back there and has done really well for them. We always knew of his abilities, good talents, mobility and a winning mentality, so I think he's improved them.
"They got off to a great start to the season and it wasn't until January that they hit a blip and that happens to everyone. They're over that now, so they'll be the threat."