Steven Gerrard says that the rest of the Premier League will be waiting to see if Manchester United 'wobble' next season.
David Moyes was announced as Alex Ferguson's successor in May and will officially start his new job on Monday.
And speaking to Sky Sports News, Gerrard says that all eyes will be on the new man.
Gerrard said: "They have replaced a world-class manager with another who has done a fantastic job at Everton, so I think David will continue to do a good job there.
"It is new for Manchester United. From a biased point of view, let's hope they have a wobble, but I think they have too many good players to fall out of the title race.
"They have world-class players and I expect them to fight for the league again."
Liverpool start their campaign with a home game against Stoke City while United travel to Wales to play Swansea City.
The left-back, 35, who has made over 500 appearances in the Football League, becomes the first signing under Bury's new ownership.
Roberts was on the books of Liverpool in his youth, winning the FA Youth Cup in 1996, before moving to Greece for a short spell at Panionios, where Liverpool legend Ronnie Whelan was manager.
His time in Greece was short-lived, however, and he returned to England to join Tranmere and played over 300 times for the Wirral club before moving to Doncaster and then Derby.
He won nine caps for Wales between 2000 and 2005.
Having signed from Everton last summer following a successful loan spell, the 21-year-old cemented his place in the Brentford midfield and went on to score the winning penalty in the play-off semi-final victory over Swindon.
"The signature of Adam is another signal of the long-term commitment being demonstrated by both the club and the individual players," Bees sporting director Mark Warburton told the official club's website.
"It is important that the club recognises and rewards the consistent level of performance displayed by Adam and the offer of an extended contract gives him the peace of mind to focus solely on his continued development as a player."
