Six months ago, Pep Guardiola's Manchester City were heralded by many as the greatest team of the Premier League era having smashed a series of records on the way to winning the 2017-18 title. They became the first team to amass 100 points in the Premier League and also won the title with a 19-point margin -- the biggest-ever.
In the end, City set 11 new records last season including most wins, most goals, most away wins and longest winning run. But as 2018 is consigned to history and with Guardiola's champions sitting seven points adrift of unbeaten league leaders Liverpool ahead of Thursday's first vs. second clash at the Etihad, those claims of City being the best ever are already looking somewhat dated.
The reality is that the challenges ahead of them, both in terms of catching Liverpool and retaining the title, are the ones that will truly define their quality and historic standing among the greats.
City were sensational last season and the 11 broken records are a testament to that, but one season can never be a true gauge of a team's strength and status. If they're unable to retain the title this season, then this City team will not be able to stand shoulder to shoulder with the Manchester United sides built by Sir Alex Ferguson, teams that won and retained titles on several occasions.
United won a hat-trick of titles on two separate occasions under Ferguson. Jose Mourinho's first Chelsea team, which won back-to-back titles in 2004-05 and 2005-06, were also able to build on a great title-winning campaign by winning again. That is the task City must pull off to prove that last season's success was nothing more than a brilliant, but fleeting, period of dominance.
Of course, it would be foolish to suggest that Guardiola and his players cannot close the gap on Liverpool and beat them to the title. Last season proved they are an outstanding team and you can bet that Guardiola and the likes of Kevin De Bruyne, David Silva, Raheem Sterling and Co. are desperate to earn their place alongside the greats of United and Chelsea by retaining the title.
City have been unable to do it on the two previous occasions they've won the Premier League, and even Arsenal's great Invincibles of 2003-04 failed to retain the title. But now is the time for Guardiola and his players to step up to the plate and secure their place among the greats.
Last season was a procession to the title and there was never any sense of City being put under pressure by the rivals. Now they are under intense pressure to deliver because any failure to beat Liverpool on Thursday would leave Jurgen Klopp's team at least seven points clear at the top. If City win, the deficit would be down to four points and they would have the opportunity to test Liverpool's mental strength by turning the screw with constant pressure on the leaders.
History is not on City's side but that only adds to the measure of greatness facing Guardiola and his players. No team has ever been as far ahead as Liverpool on New Year's Day and failed to win the title. The biggest lead overturned from this stage of the season has been five points; overtaking Liverpool's current seven-point lead would constitute a huge achievement by City.
United trailed Arsenal by five points with 12 games to play in 2007-08 but still went on to catch Arsene Wenger's team and retain the title. In 1995-96, Newcastle surrendered a 12-point lead over United in February to finish second behind Ferguson's team, but United haven't been immune to their own collapses, with Arsenal erasing an 11-point deficit over the final 10 games of the season to win the title in 1997-98. In 2011-12, United led by eight points with just six games to play but City won the title on goal difference thanks to Sergio Aguero's stoppage-time winner against Queens Park Rangers on the final day of the season.
The challenge for City is clear: they must rewrite history once again to hold onto their title by making Liverpool throw away their seven-point lead. But it is a challenge that great players should relish and one that, if achieved, is likely to give them an even greater sense of satisfaction that their record-breaking success last season was not a fluke.
Guardiola's City have shown us how they can tear teams apart with their champagne football and ruthlessness in front of goal, but overcoming adversity to beat an imposing challenger would surely be a truer measure of greatness. Klopp's Liverpool look unstoppable right now but if this City team is the greatest in Premier League history, they have the perfect opportunity to prove it between now and the end of the season.
If they can finish top of the pile ahead of this Liverpool team, nobody could then question the greatness of Guardiola's City.