Sir Alex Ferguson believes that Manchester United now have four Premier League title rivals this season after identifying Liverpool as capable champions again.
Liverpool have spent big so far in 2011, following the captures of strike duo Andy Carroll and Luis Suarez, winger Stewart Downing and central midfielders Jordan Henderson and Charlie Adam.
This heavy investment is largely expected to allow Liverpool to make their biggest title challenge in three seasons after they finished second in the 2008/09 campaign.
The last two seasons have been full of under-achievement at Anfield, as Liverpool have failed to finish in the top five and have got no nearer than 22 points from top spot in the final Premier League standings.
Sir Alex is sure that Liverpool will pose a greater challenge this season, alongside the usual title suspects Chelsea, Arsenal and Manchester City, although he does not believe Tottenham have a strong enough squad to pose a threat.
The Manchester United manager said: “One of those four will always be a thorn in our flesh. They are our immediate challengers. No matter where it comes from, somewhere along the line we are going to be faced with a big challenge from one of those four great clubs.
“Liverpool went off the radar for a bit. They are now back on it. Long term you know they are going to there.”
With just under a month to go until the start of the new season, Liverpool still have time to strengthen their squad further and Kenny Dalglish is still in the market for a new left-back after missing out on Gael Clichy.
However, Aly Cissokho is unlikely to arrive from Lyon.
Liverpool remain at 10/1 in the Premier League odds to win the title this season, while it is 1/1 that they at worst break back into the top four.
Manchester United are the title favourites at 7/4, with Chelsea the next best at 5/2 and Manchester City 7/2.