Michael Owen believes Manchester United could learn a lesson from arch-rival Liverpool after claiming Ole Gunnar Solskjaer's players are "at best staying still, but most of all regressing."
Already seven points behind Premier League leader Liverpool after just four games of the season, United takes on Leicester on Saturday having managed just one victory so far this term.
Owen, who played for both clubs during an illustrious playing career, believes the ability of Liverpool coach Jurgen Klopp to improve his players and take them to the next level has been a key part of the team's success.
While Liverpool ended last season by finishing second in the Premier League and winning the European Champions League, United recorded a sixth place finish, 32 points adrift of champion Manchester City.
And Owen says Klopp's coaching and ability to constantly draw the very best from his players is something United should take note from.
"To me, if you look at Liverpool five years ago and you've got some players that have come from lesser teams let's say, and Jurgen Klopp has come in and improved every single one of those players," Owen told CNN.
"All those players in the Liverpool squad now you think 'wow, you're playing at the peak you've ever played at in your career. He's almost improving players, he's improving the team, he's got a feelgood factor and it's quite the opposite at Manchester United for the last five or six years.
"Players are going there and at best staying still but most of all regressing."
Owen, who scored 17 goals in 52 games for United between 2009-2012, cites the failures of big-money signings Angel Di Maria and Alexis Sanchez, both of whom have since left, and the sale of Romelu Lukaku to Inter Milan as part of a trend in which the club fails to coax the best from its big name players.
Paul Pogba, who re-signed for the club from Juventus for a reported fee of $115 million in August 2016, three years after leaving for just $1.9 million, has also been fiercely criticized for his performances.
"You look at the great Di Maria, Sanchez, they've both been brought in for huge investment and let go pretty much straight away," added Owen, who has just released his autobiography, "Michael Owen Reboot -- My Life."
"You've got Pogba, arguably one of the best players in the world, that people still have the jury out on.
"You've got Lukaku who came, gone. Big money, he's gone. Virtually every player that they bring [in] either going straight back out the door or is regressing.
"Now I don't think that's just a coincidence. I think there has to be something whereby, put it this way, if Jurgen Klopp was the manager or Pep Guardiola was the manager at Manchester United over these last five or six years, I think they have players who are virtually equal but the best isn't being gotten out of them and that's the big key for Ole Gunnar Solskjaer."
Di Maria arrived in Manchester for £59.7 million ($73.7 million), a then British transfer record when he signed from Real Madrid in 2014. He lasted just a year before moving to Paris Saint-Germain for £44.3 million ($54.7 million).
Sanchez, reportedly one of the club's highest earners, left on loan to join Inter Milan last month. He endured a difficult 19 months at Old Trafford after joining from Arsenal, scoring just five goals in 45 appearances.
He has teamed up with Lukaku, who signed for Inter in a deal worth £74 million ($90 million), last month. The Belgian international, who joined United two years ago from Everton in a deal worth £75 million ($91 million), scored 42 goals in 96 appearances for the club.
Lukaku's departure has left Solskjaer light in the striking department with added pressure on Marcus Rashford and Antony Martial.
While United spent heavily at the back, coughing up a reported £79 million ($97 million) for England international Harry Maguire, a world record fee for a defender, and £50 million ($62 million) on full-back Aaron Wan-Bissaka from Crystal Palace, it did not replace Lukaku.
Contrast the attacking resources at Solskjaer's disposal compared to those enjoyed by Pep Guardiola at Manchester City and Klopp at Liverpool, and it's not difficult to see why United may struggle to keep up with their Premier League rivals.
"He's got to find a way of getting the best out of these players," Owen said of Solskjaer's squad.
"You can't just keep losing a game, right, let's go and sell him, sell him, and bring the next superstar in, spend another £80 million.
"You know, that's been happening for half a dozen years now. Alexis Sanchez was the best player in the Premier League for three seasons. All of a sudden he turns up at Old Trafford and he's just a pale shadow of what he was.
"There's so many examples. I don't think you can keep looking at players and say, 'oh yeah, they're not good enough, let's bring new in' and keep doing that. It would cost a fortune for starters but you need to looking a bit more within as well."