By Greg Lea.

If any further proof was needed of how quickly things can change in the world of football, Inter's downturn in fortunes in the last couple of months provides a perfect case study.

When Serie A resumed in early January after a two-week winter break, Roberto Mancini's men found themselves a point clear at the top of the table, with their first 17 matches yielding 11 wins, three draws and only three losses. A few short weeks later, Inter have fallen below Juventus, Napoli, Roma and Fiorentina and into fifth place, with a hefty margin of 13 points now separating them from the summit of the standings.

They have won only two of their last nine outings a run that has featured draws with Carpi, Atalanta and Hellas Verona and defeats to Sassuolo and dreaded rivals Milan with Sunday night's 2-0 reverse at the hands of Juventus in Turin meaning there has been a 21-point swing away from Inter and towards the Bianconeri in just 19 Serie A games. All of a sudden, Champions League qualification, let alone a 19th Scudetto, is beginning to get away from the Nerazzurri.

In order to understand what has gone wrong since the turn of the year, it is necessary to first consider the key reasons behind Inter's success before Christmas. Mancini's men's major strength was their defensive solidity: 12 clean sheets were recorded in their first 18 fixtures including against Juventus, Milan and Roma with just 11 goals conceded and eight of their matches ending in 1-0 wins. Joao Miranda and Jeison Murillo formed a promising partnership in the heart of the backline, with the midfielders ahead of them offering the defensive line plenty of protection. There may not have been a great deal of creativity on show, but Inter proved adept at grinding out victories and picking up points by any means necessary.

Since the start of the calendar year, however, Inter have begun to leak goals: 17 have been conceded in their nine games in 2016 to date, over 50 per cent more than they let in those first 18 games before the winter break. Inter have struggled to score all season only two of their last 11 Serie A encounters have seen them find the back of the net on more than one occasion and have therefore been unable to bridge the gap now that they are displaying far more vulnerability at the other end of the pitch.

As well as simply lacking enough creative players, particularly in the centre of midfield, Inter have been undone by Mancini's excessive tinkering, which has seen the side line up in different systems and formations almost every week. While tactical adaptability should generally be applauded as a positive attribute, the regularity with which Inter have chopped and changed has harmed their ability to build up any sort of rhythm and cohesion.

There may still be 11 games remaining in the campaign, but the momentum looks to be against Inter at present. With Juventus and Napoli almost certain to finish in the top three, there is just one more Champions League spot up for grabs on the peninsula; Fiorentina and Roma look in far better shape to obtain it, and even Milan now just a point behind their neighbours are likely to fancy their chances of finishing ahead of Inter the way things are going for the duo at the moment.

Two months ago, Inter's title challenge was very much alive and kicking. In football, though, an awful lot can change in a relatively short space of time.