Sergio Aguero's double, either side of an Adam Johnson effort secured a 3-0 win for the Blues on Wednesday evening but despite their form in the Barclays Premier League they were knocked out of the Champions League at the group stage.
And Pulis believes that is a cause for regret, saying: "They must be distraught they are out of the Champions League. I thought they would have run that very close this year, never mind the Premier League. They are real contenders for every competition they are in."
He added: "The depth of their squad and the quality they have got is what you would expect after spending ?240million, or whatever it is."
Overcoming the side that beat Stoke in last season's FA Cup final was too much for Pulis' men on Wednesday night.
Aguero was named man of the match for another outstanding contribution, taking his seasonal goal tally to 15. However, there were plenty of other contenders too.
"Sergio scored two goals but all the players did very well," said Mancini.
"I am happy to be at the top at Christmas. I am happy for our supporters. They can have a good Christmas Day.
"But as I have said many times, it is important to stay there for the rest of the season. For this, it is difficult. United continue to win every game, the other teams continue to win; Arsenal, Tottenham.
"But it is better to stay on the top than second."