Ole Gunnar Solskjaer says Manchester United have been a major disappointment since the retirement of legendary manager Alex Ferguson and described their battle for fourth place as "undignifying".
Ferguson oversaw a period of unrivalled success in English football during 26 years at Old Trafford, but United have failed to build on his legacy since he stepped aside at the end of the 2012-13 Premier League campaign.
Immediate successor David Moyes lasted less than 12 months in the role and United failed to qualify for the Champions League in their first season without Ferguson at the helm.
Louis van Gaal orchestrated a return to Europe's top table by overseeing a fourth-placed finish last term, but the Dutchman has faced severe criticism over a perceived negative style of play and United are six points off the Champions League places in fifth this season.
While United can still make the top four, Solskjaer - who won the Premier League six times during an 11-year stay at Old Trafford - is saddened to see that as the club's league objective.
"I am very disappointed in the quality over the past few years," Solskjaer told Fotbollskanalen. "We knew it would be tough after the Ferguson era but we have not managed to keep the enthusiasm and the entertaining, attacking football.
"It is very tough to see Manchester City managing to get Pep Guardiola and sign the biggest stars in Europe. I am a big fan of Guardiola and his philosophy and all his teams.
"United have to pull themselves together. They are heading for a very difficult time. We are used to winning. We are used to finishing first. We are used to entertaining the fans.
"If we finished second it was a disappointing season, now the talk is about finishing fourth. It is undignifying for a club like Manchester United."
Van Gaal's difficulties in the hot seat have led to speculation the Dutchman could be sacked, with Jose Mourinho heavily linked with the position while club legend Ryan Giggs - United's assistant - is also a reported candidate for the top job.
However, Solskjaer does not expect the club to dismiss Van Gaal, regardless of their difficulties this season.
"I think Van Gaal will stay for three years," he added. "It is a plan and a process and I am 100 per cent sure he will stay for three years.
"Ryan Giggs is the most likely former player to manage the club. He has Manchester United DNA in his body."