Chelsea v. City A-Z Pt4  (Sky Sports)

In the last of our four-part series, we look at the reasons why Chelsea and Man City have stolen a march on their rivals in the title race...

T is for Terry

After Chelsea conceded 17 goals in their first 15 matches of the 2013/14 Premier League season, Jose Mourinho joked that even the training dummies could score against his team. John Terry's form was thrust into the spotlight following successive gamnes in which the Blues conceded three goals - a 4-3 win at Sunderland and 3-2 defeat to Stoke - with doubts over the defender's long-term future at Stamford Bridge.

However, when the pressure was on Terry again rose to the challenge, sparking a significant improvement in Chelsea's resolve to coincide with his own. The Blues shipped just 10 more strikes in the remaining 23 matches, marking a drop from 1.13 to 0.43 in the average number of goals conceded per game.

Now 34, the Chelsea captain has maintained his form in the current campaign, prompting effusive praise from Mourinho in November. "He's full of confidence. I see my John of 2004, 05, 06," said the manager. "I don't see any difference. I only see a difference when his twins are on the training ground. They were born in that period and now they are running and kicking balls."

Terry's leadership has been vital in Chelsea achieving the second-best defensive record so far, while he has also had a big influence in Gary Cahill establishing himself as one of England's strongest defenders and Kurt Zouma emerging as the next young star at Stamford Bridge.

U is for Unity

When asked what differences to the previous season ensured City's title-winning success in 2013/14, Samir Nasri said: "It's the atmosphere in the dressing room. We've really been friends this year. Everyone put ego to the side and we worked for the squad. At some points we were behind but we kept believing."

During Roberto Mancini's reign in 2012/13, there were rumours of unrest among the City squad, with images of the manager wrestling Mario Balotelli on the training ground printed in the papers. Those whispers quickly disappeared following Manuel Pellegrini's appointment, however, and the new-found harmony at the club helped secure a second Premier League crown in three years.

Similar to Pellegrini, one of Jose Mourinho's leading achievements has been developing stronger bonds at Stamford Bridge following the discord under Rafa Benitez's and Andre Villas-Boas' tenures. He has occasionally relied on a siege mentality to expedite this process, but the manager's success was seen in the relatively muted reaction to the departure of club legend Frank Lampard. Both the players and the fans clearly trust Mourinho, which has been key in building unity.

V is for Vincent Kompany

For Terry at Chelsea, read Kompany at Manchester City; a towering vocal presence at the back driving his team-mates forward.

While injuries have hindered the captain's consistency this season - with occasional questions over his decision-making - his influence both on the pitch and around the club in general cannot be disputed. Along with Pablo Zabaleta, the Belgian has been to glue holding City together in their new era of enormous investment and top-level competition, providing a firm focus on the football to contrast with talk of 'projects' in the boardroom.

Although City were perhaps rather lucky to escape with a 1-1 draw when they faced Chelsea at the Etihad in September, Kompany earned plenty of praise for a dominant display against Diego Costa. After seven strikes in his first four matches, the Spain international was barely allowed a sniff - managing just one shot on target and being dispossessed three times more than any other player - with Kompany aiming to deliver another show of strength on Saturday.

W is for Winning Runs

Liverpool's brilliant 11-match winning streak almost carried them to the title last year, but Manchester City have been much more consistent in building momentum over the past five-and-a-half seasons.

The champions laid the foundations for their title success with eight consecutive victories between December 2013 and January 2014, and were close to matching that record this season with seven successive wins over November and December. In total, six of the 12 longest winning runs since 2009/10 have been recorded by City, playing a significant role in their two Premier League crowns.

Chelsea's longest run over the same period is eight wins in their triumphant 2009/10 campaign, while they have also managed two 14-game unbeaten streaks during Mourinho's second coming in which they twice gained 36 points out of a possible 42. If the Blues produce similar form between now and the end of the campaign, it will be enormously difficult for City to bridge the five-point gap at the top.

X is for X Factor

X factor, the product of all these combined qualities that leaves Chelsea and City embroiled in a two-way battle for the title as their rivals struggle to keep up.

Mourinho's Chelsea teams have been tainted with accusations of uninspiring football in the past - notably by Manuel Pellegrini and Brendan Rodgers last season - but at their most fluent there are few better sides to watch.

The recent 5-0 victory over Swansea is a perfect example of the Blues' brilliant intuition and creativity as they emphatically brushed their opponents aside with a relentless, comprehensive display. 'Omg how well @ChelseaFC is playing today...That is such a great football,' tweeted academy product Lucas Piazon afterwards.

Along with Chelsea's thrashing of Swansea, City's 4-1 victory against Tottenham should go down as one of the most complete Premier League performances of the season, while the champions saw off third-place Southampton with a minimum amount of fuss at St. Mary's in November.

Great teams bring enormous expectations and excitement and, having scored the most goals in the division so far (Chelsea on 51, City on 45), the top two are certainly on every weekend's must-watch list.

Y is for Yaya Toure

Although Toure will miss Saturday's crunch clash at Stamford Bridge owing to his Africa Cup of Nations involvement, the midfielder remains one of the driving forces behind City's title challenge, chipping in with seven goals in his 18 appearances.

After a somewhat slow start to the season overshadowed by personal problems, the 31-year-old has kicked on in recent months, scoring in six of his last eight Premier League matches and grabbing the winners against Swansea and Everton.

Toure proved to be City's clutch in both their recent title successes - scoring seven goals in the run-in last season and both strikes in the crucial 2-0 win at Newcastle in May 2012 - and Manuel Pellegrini will hope he's soon up to speed following his return from Equatorial Guinea.

Z is for Zabaleta

Pablo Zabaleta's tireless efforts down City's right flank are emphasised by two telling statistics: Firstly, only three top-flight players (Nathaniel Clyne, Lucas Leiva and Nemanja Matic) have averaged more tackles per game, and secondly, the Argentinean has made more assists than David Silva, Sergio Aguero and Yaya Toure this season.

A first-team regular since signing for just £6m in 2008, Zabaleta also scored the second goal away to Roma in the Champions League as City secured their late progression to the knock-out stage.

As one of the most consistent two right-backs in the division, along with Branislav Ivanovic, the 30-year-old will be up for the tough test against Eden Hazard at Stamford Bridge. The Belgian will have to be wary of his opponent's eagerness to support the attack if Chelsea are to avoid being caught out.