Sir Alex Ferguson says Paul Lambert has a daunting task ahead of him at Villa Park as the sides prepare to face each other on Saturday evening.
Villa, who hover one place above the relegation zone, picked up consecutive victories for the first time this season following their League Cup win over Swindon and 1-0 victory at Sunderland.
But with Lambert the eighth man to take the reins at Villa Park during the last decade, Ferguson believes a change of managers must have an effect on the team's performances.
"Paul Lambert is a new manager there," said Ferguson.
"It's a big task and a daunting one as Villa are not where everyone expects them to be.
"If you look at the team, it's a completely new team: a new back four, a new midfield and a new striker from the Belgian league [Christian Benteke].
"It does take time to change teams. When you've got that many new players, it's hard but Paul has done well as a manager and is still young.
"Villa have a great history of course, winning the European Cup in 1982 by beating Bayern Munich, having won the league the year before.
"I think it's probably correct to say they haven't matched their expectations over the years.
"When we pipped them to the title [in 1992/93], that was a good team, but you wonder if the managers changing has a big effect on the playing standards of the team. They've had quite a few managers over the years."