Roy Keane claims lack of experience in the back four and injuries to defenders will see Manchester United struggle to win major silverware in the next few years.
The Old Trafford club are fourth in the table with 11 points after seven games and trail league leaders Chelsea by eight points.
The Red Devils struggled last season as they finished seventh in the league table under David Moyes' guidance for most part of the season.
The Scot was replaced by Louis van Gaal and the Dutchman has also endured a tough start to this campaign.
United's three first choice defenders Phil Jones, Jonny Evans and Chris Smalling are recovering from injury and their inexperienced back four has been exposed in the league.
However, the 20-time English champions have one of the best attacking line-ups in England. The list includes summer signings Radamel Falcao and Angel Di Maria, along with Wayne Rooney and Robin van Persie.
The former United skipper believes the Red Devils are still "a few years away" from winning the title, despite having world class players on the attacking front.
"It's been a bit better these last few weeks. Clearly they are going to win lots of football matches because they've got lots of goals in their team now. Going forward, the players they have available - amazing," Keane told BBC.
"But, in terms of winning the bigger prizes again - the Premier League and Champions League - I think that might be a few years down the road yet. Only in a sense that defensively they look to rebuild."
"You can win football matches going forward, with lots of goals, but I think at the back with the lack of experience, and injuries problems at the moment, it will be very hard to win titles," the United legend added.
Injuries have not helped Van Gaal to settle quickly in the Premier League. The former Netherlands manager is currently without the services of key players like Michael Carrick, Jones, Evans, Smalling and midfielder Ander Herrera.
Carrick is likely to return to action for United's upcoming clash against West Bromwich Albion, while he would also be joined by centre-back Jones.
The return of several key players could help United finish in the top three and qualify for next year's Champions League.