Ex-Everton boss David Moyes succeeded Ferguson in the off-season, with his predecessor collecting two European Cups and 13 Premier League titles among many other honours in an unmatched 27-year spell at Old Trafford.
Under Moyes, however, the English champions have made their worst start to a season since 1989, as they lie 12th in the domestic standings with seven points - eight points adrift of leaders Arsenal after six rounds of fixtures.
While the Red Devils earned a creditable 1-1 away draw with Shakhtar Donetsk in the Champions League on Wednesday night, player-coach Giggs concedes they need to raise their game.
"Sir Alex was a great manager and a great influence on the team and the club. You are going to miss someone like that," said the 39-year-old midfielder.
"But I don't think that is an excuse when individuals aren't playing as well as they can. We are not playing well as a team.
"We haven't got injury problems as we have had in the past. There is no excuse.
"It hasn't been a great start to the season but the good thing about that is we have plenty of time to turn it round.
"We know what this club is like, it is ups and downs and we don't get carried away if we are flying and we don't get carried away when we are not playing well.
"I can't put my finger on what has happened. We have just not played as well as we can, both individually and as a team.
"The results have shown we haven't played as well as we can do. But we know the quality in the dressing room.
"We're the champions so we showed that quality last year and we have to show it again."