Manchester City, Manchester United in heated Premier League scrap

With the £40 million signing of Nemanja Matic, Manchester United and Jose Mourinho may have achieved two things in one fell swoop: to create the tallest side ever to step out in the Premier League and to hoist themselves into serious contention for the title.

Manchester City's great rivals have been fighting a desperate battle over the last four years not to go the way of former dominant English champions Leeds United and Liverpool. Thus far it has proved an expensive and painful struggle.

With the two aforementioned clubs firmly in mind (Leeds, overwhelmingly England's best in the early '70s, and Liverpool, who obliterated all-comers for a decade-and-a-half between 1976 and 1989), United have been fighting tooth and nail not to be surpassed and forgotten by the likes of Chelsea, City and Tottenham.

City, of course, are United's worst nightmare. When Sir Alex Ferguson uttered the famous words "not in my lifetime," he was referring to the resounding belief City would never edge ahead of his beloved United within the foreseeable future. The "noisy neighbours" tag was also invented as a direct put-down to a club that he considered not "classy" enough to supplant his United empire.

At the time many thought the words well-chosen, if a little disrespectful. City had been used to this for decades, while United ruled the roost throughout the '90s. The better United got, the worse City became, drifting off to such a level of football and financial poverty that most people even began to forget that they existed as a relevant threat. Indeed, wallowing in mid-table of the third tier of English football tended to prove the naysayers right. City were truly no longer worth worrying about.

With United comfortable at the top, having "knocked Liverpool off their perch," as Ferguson had famously craved, City supporters had to endure decades of put-downs and jokes at their expense.

Leeds -- and to a significantly lesser extent, Liverpool -- have discovered how it feels to become irrelevant to matters at the top of the football tree, but they had at least enjoyed their time in the spotlight. City spent 1975 to 1982 in United's shadow, before beginning two decades of relegations and promotions that tested the patience of every fan that ever set foot inside Maine Road or Eastlands.

Then came the seismic shift: Saturday, April 16, 2011.

The FA Cup semifinal between the two Manchester clubs finally brought relief to the blue half of the city and a subsequent first trophy in 35 years, against Stoke in the final. But it was the defeat of their neighbours that resonated most, producing a tidal wave that has swept United on to the second tier of Manchester football affairs.

Since that momentous occasion, City have travelled to Old Trafford and come away with 6-1 and 3-0 victories -- utterly unthinkable in the previous four decades -- and have claimed two league titles of their own. Much, one would imagine, to Ferguson's chagrin. In this particular equation, however, the respective league positions of the clubs underlines the shift best of all. When United lost to Tottenham last May, thus making it impossible for them to finish above City for the fourth consecutive season, a record that had held firm since 1975 was broken. It was that year that City last finished ahead of their rivals for a fourth consecutive season, one of which had actually seen United in the second division.

Since winning their last Premier League title in 2012-13, United have finished seventh, fourth, fifth and sixth, respectively -- six, two, one and three places adrift of City. The significance of this will not only have sunk in with such luminaries as Ferguson, but far wider afield too.

City's turnaround and United's demise have been rendered starker for their coincidence. Just as United have floundered, so City have prospered. In fact, some might say that -- to a degree -- City's surge toward the top has partly caused United's downfall. As with Chelsea before, City's arrival in the top four has helped upset the old equilibrium.

First Liverpool found themselves dispelled from the old Champions League cartel, and now it is United finding it tough to maintain a presence. The Europa League win over Ajax last May has allowed Mourinho's men a back door entrance into the big league again. To keep hold of it they will need to secure a top four place in the coming season's Premier League.

Everything points to a fascinating jostle for position. Within that struggle, City and United look set to produce a head-to-head race that has only really been seen twice before: in 1968 and again in 2012. On both occasions, City finished as league champions and United as runners-up. If the big bucks spent by Mourinho and Pep Guardiola are to have the desired effect, 2017-18 must produce something similar and a return to a seething, closely fought rivalry between Manchester's big two.