Pochettino was critical of his players' failure to hold on to the lead given to them by Abdoulaye Doucoure's 53rd-minute own goal.
Pochettino warned his players before their trip to Watford that they would "crash" if they got carried away with their victory at Old Trafford. By comparison, Manchester City squandered 11 points, United 12, Chelsea 19, Arsenal 29 and Liverpool under Jurgen Klopp a remarkable 34.
He continued in his press conference: "It is of course so painful to concede two goals like this, so painful that the first half looks like a friendly game".
"After you win the game [against United] I think you need to respect more this competition", Pochettino told the press.
Spurs remained in the ascendancy but as the game approached the final quarter, Watford began to build a head of steam and came agonisingly close to an equaliser when Alderweireld headed against his own bar from a Deeney cross.
But they go into the global break on the back of a defeat away to Watford and there are still a numbers of first teamers that need to improve this season to turn them into title challengers.
"If you want to be a contender you can not concede the type of goals we conceded".
"Today, it's good to compare".
"But before we talk, we need to show that we are contenders, and how (do) you show?"
The Denmark playmaker said: "We're very disappointed". I was more upset after Monday'.
Tottenham has proven to be very good on the road and they have much more talent.
"We have therefore agreed with the Premier League that, in the interests of clarity and certainty, we shall confirm this game as taking place at this time at Wembley Stadium so that fans of both teams can now make travel arrangements accordingly".
"We need to get back on track and do that against Liverpool".