United had beaten City in a stunning comeback during the derby, denying them the title, but denied that win was the most important win of the season.
Mourinho's men struggled to combine in first 10 minutes of the second stanza and needed to increase their tempo to create chances.
"I won eight titles and I'm not in the moon because I won against Manchester City, a match that is just three points", he said.
They have dominated this year's title race, scoring 93 goals and losing just twice so far.
"I know that you don't want to read anything after a defeat like this one, that any comments made after the game sound like hollow words".
For all of United's class recently and across season in general, it was a calamity of errors and an unwanted punchline to their campaign. "The Premier League is so, so tough".
United now will look to secure second place and build on a slightly disappointing season which saw José Mourinho struggle to get the most out of a very talented squad.
The Portuguese was unimpressed with his players' efforts and attacked their lack of fluidity and desire to take too much touches.
Now the United boss has called on Pogba to produce more displays like that - and he says the hard work must start in training at Carrington.
"I know them, I smell, I have lots of experience and that's not me".
"He told them be careful it is going to be different against West Brom and I go back to Pogba: why didn't you and the rest of the team do what you did against City all season?". But I expect you to be consistent in a certain level.
Jake Livermore forced a smart save out of David De Gea on 12 minutes with a left-footed shot from 12 yards out after being played in on the right by Salomon Rondon, who steered a header well over the target from James McClean's cross on the left moments later.
United midfielder Nemanja Matic had headed a corner across his own goal area and Rodriguez reacted quickly to nod home the victor. I was not going to celebrate like insane, for me we should play with great focus and intensity and try and kill the top four situation and be more stable in second.
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