Manchester United crushed derby rivals City 4-2 at Old Trafford on Sunday. PA Sport looks at four lessons learnt from the match.
1 Crisis for City and Pellegrini
Man City's results since going joint-top of the Premier League on New Year's Day make abysmal reading for a side of their quality.
Their run of four league wins in 12 games - during which they also went out of two cup competitions - surely constitutes a crisis for a club with their expectations.
The already considerable scrutiny on manager Manuel Pellegrini will increase another notch.
2 Fellaini continues to hit back
For much of his first season at United, Marouane Fellaini looked out of touch and possibly out of his depth.
That has all changed in the last few months as he has become increasingly important to Louis van Gaal. The midfielder uses his strength to great effect as United continue to loft the ball forward to him and teams find him difficult to dispossess.
3 City team coming to end of line
There can be little doubt that the City team, the core of which have won two EPL titles, an FA Cup and a League Cup, are coming to the end of their lifespan. Reinvestment is clearly needed in the summer and, on this evidence, the back four would be a priority.
4 United need to improve defensively too
Although United went on to dominate the game, City started superbly, reminding everyone of the quality they do still possess.
They troubled United repeatedly at the back, where the central defensive partnership of Chris Smalling and Phil Jones again looked vulnerable.