Local derbies could have a big influence on the outcome of the English Premier League title race, and they don't come much bigger than tomorrow's clash between Liverpool and Manchester United. It may not be a one-city rivalry, but it is bitter, fierce and usually contested for high stakes.
The showdown at Anfield is no exception and the atmosphere will be heightened by the problems swirling around Liverpool and their manager, Rafa Benitez. United have a good recent record at Anfield and their fans will be relishing the prospect of inflicting a fifth straight defeat on Liverpool, which might be a fatal blow both for Benitez's title hopes and for his job.
The crisis at Liverpool has been deepened in recent games by the absence of their two key players, Steven Gerrard and Fernando Torres, and the return of one or both of those talismanic figures could hold the key to their chance of bouncing back to form in this massive game.
Yet it is possible to read too much into that factor, because Liverpool won this fixture 2-1 last season without Gerrard and Torres in the starting line-up, though Gerrard did come on in the 68th minute with the scores level. Then, however, Liverpool had Xabi Alonso in tandem with Javier Mascherano to anchor the midfield and make Liverpool more secure than they have looked so far this season.
Each sector of the Liverpool side has shown vulnerability this season, from a defence that has kept only two clean sheets in nine league games to a midfield that looks less solid and an attack that lacks creativity when Gerrard and Torres are absent or not on top form.
Last season Liverpool had 20 clean sheets in 38 league games, so clearly their problems start at the back. Professional analysts are divided over the merits of their zonal marking system but, whatever your view on that, a clear lack of confidence in the defence has let them down this season.