The title race is all but over with Manchester United 15 points clear of City, but the derby will still attract plenty of attention after the drama of December's edition.

Both Roberto Mancini and Alex Ferguson have cited Robin Van Persie as the key difference between the teams this season and it was his free-kick which swung December's derby match in United's favour.

His recent goal drought aside, has his contribution been quite as decisive as portrayed this season?

RVP

Last season, Manchester City won the title on goal difference, scoring 93 league goals or 2.45 goals per game.

Manchester United found the net 89 times (2.34 per game) in 2011-12 as they lost out by eight goals and Ferguson vowed to avoid a similar situation occuring this season.

With Van Persie on 19 league goals (Rooney is the next highest scorer for United with 12) the Reds have scored an impressive 70 league goals in 30 matches or 2.33 per game compared to City's lowly 1.83.

Overall, United's goal rate is almost identical to last season but RVP's impact has been stark in the sense that it masked the Reds' poor defensive record from earlier in the season.

United may have kept eight clean sheets in 11 games since their fortunate 4 - 3 victory over Newcastle on Stephen's Day, but they have still conceded 1.03 goals per game compared to 0.87 in 2011/12.

But up to and including that win over the Toon, United had conceded 28 goals in 19 games. But in contrast they had been free-scoring, finding the net 48 times, with Van Persie scoring 13 of those including the winners over Southampton, Liverpool, Reading, West Ham and Man City.

City's scoring struggles

City's comparitive drop in the goal stakes has also been key this season and is related to the team's lack of width.

Mancini experimented with a back three and wing backs earlier in the season, but for the most part he has favoured a 4-4-2 with David Silva and Samir Nasri out wide. Both players - although talented - prefer to cut inside rather than expand the field which leaves City's attacks quite narrow.

However, full-backs normally provide the bailout in those situations. But Pablo Zabaleta and Gael Clichy have not been efficient in the final third. 

Zabaleta has only provided two assists and 15 chances in 25 games despite being a willing runner, while Clichy has the same number of assists and created just 17 chances in 23 matches.

That lack of guile explains why more than half of City's goals (28) have come in the last half hour of games when desperation rather than fluency kicks in.

Defences

United's defensive problems earlier in the season are well documented but they have managed to turn that around with eight clean sheets in their last 11 matches, a run which has seen them concede just three times.

Nemanja Vidic's return to fitness and Jonny Evans, Rafael Da Silva and David De Gea's rapid developments have been key but so have tactical tweaks at the other end of the field. 

Cavalier in the first half of the season, Ferguson - with a couple of exceptions - has refrained from starting more than two of his four forwards in the league which has given the team a greater level of balance.

That balance has also been aided by Phil Jones' return from serious injury. Not technically brilliant on the ball, he is a strong competitor in the middle of the park.

Meanwhile, City still have the best defensive record in the league but they have been slightly more porous this season.

Last term, the Sky Blues conceded 0.76 goals per game compared to 0.86 in 2012-13. But it has been mistakes at key moments that have been most apparent with Joe Hart particularly culpable despite his portrayal across the water.

He and his team have conceded 35 per cent of their goals from long range, while just one of United's 31 has come from outside the box.

City need the win more so they may be tempted to throw down the gauntlet from the beginning. But with a lack of first half goals, Mancini will need to find a way to get past that flaw.

United's new found defensive resilience will allow them to soak up pressure, which means the match may be quite cagey in the first 45 minutes.