United went 2-0 down at half-time and a second-half red card by Harry Maguire only made things worse in the Premier League clash on Saturday.
Some Manchester United players were training at Carrington during the recent international break, while many were away with their national teams.
Manchester United have nine Premier League games and two Champions League fixtures to play between now and 30th December.
It is interesting to note that Mane is the third African player to score 100 times in the Premier League.
The Egyptian netted the Reds' fourth in the win at Vicarage Road when he beat three Watford players before producing a clinical finish.
Sadio Mane netted his 100th Premier League goal, Mohammed Salah converted an absolutely world-class finish, and Roberto Firmino bagged a hatrick in what was a perfect night for the...
The Portugal forward netted 13 times in his 30 appearances for the Reds in 2020-21 having moved to Anfield from Wolverhampton Wanderers.
Having been involved for Brazil against Uruguay in the early hours of Friday, the duo will travel directly to Spain ahead of Tuesday’s Champions League tie with Atletico Madrid.
Claudio Ranieri, who has been appointed as the new Watford manager on a two-year deal, will prepare his team to face Liverpool on Saturday.
Liverpool resume their campaign by traveling to Vicarage Road to take on Watford, who last week installed Claudio Ranieri as their new head coach.