Are Real Madrid ready for life without Cristiano Ronaldo?

This is the era of the big three. For the last five years or so, Barcelona, Bayern Munich and Real Madrid have been the dominant competitive forces in European soccer.

They've collectively reached the semifinals of the Champions League 13 out of a possible 15 times. Only Barcelona, in 2013-14, dealing with struggles brought on by the post Pep Guardiola, pre Luis Enrique interregnum, and Bayern Munich in 2010-11 just before their ascendancy began, were eliminated before the final four over that stretch of time.

Four of the last five tournaments were won by the big three, with only an incredibly unlikely Chelsea championship in 2011-12 keeping it from being a clean sweep for the three super clubs. For five years now, it's been Barcelona, Bayern Munich and Real Madrid.

But there may be cracks at the top. Real Madrid's struggles this year have been persistent enough to raise questions about whether they'll continue to be a member of that super elite group.

The tricky thing about judging Real Madrid in La Liga is that they are almost entirely viewed through the lens of their competition with Barcelona at the top. Saying Real Madrid aren't as good as Barcelona isn't a criticism, and it certainly doesn't disqualify Madrid from being one of clearly the best three teams in the world.

It's also easy to forget that while Barcelona won the treble last year, and Real Madrid won nothing, the difference at the top was only two points. It's not about being worse than Barcelona, it's by how much.

You could forgive Madrid for not keeping pace with Barcelona, a team who look set to finish with 98 points. Madrid, meanwhile, are on pace to score 81. That would be their lowest point total since 2008-09.

Madrid not only trial Barcelona by 12 points, they are behind Atletico Madrid by four. It's pretty difficult to see Real Madrid as members of an elite club that their crosstown rivals don't belong to -- if they end up finishing behind those rivals for the second time in three seasons.

Indeed, 28 games of league soccer don't make a crisis, but they should, at the least, set off some alarm bells. Real Madrid's attack, buoyed by running up some particularly auspicious goal totals, like Saturday's 7-1 pasting of Celta Vigo, remains one of the best in Spain.

They lead the league in goals with 81, though that total is a huge chunk above their 67.5 expected goals. It's possible they are just killing it at skilled finishing this year, or that their habit of running up the score produces goals against demoralised opponents whose defences aren't as present as an expected goal model might expect, but there's nothing wrong with the 67.5 number either, a figure which is the second highest in La Liga.

Defensively, things are a different story. They've conceded 27 goals which is a perfectly respectable number, the fourth fewest in the league. But a good deal of that is thanks to a tremendous season from keeper Keylor Navas.

Good Madrid goalkeeping has single-handedly been responsible for the difference between the 27 goals conceded and an expected goals conceded tally of 38, the 10th best number in the league.

Goalkeeping numbers like that are great, but even the best keepers in the world won't be able to keep up that pace. It's particularly alarming to see underlying defensive numbers that average, despite the fact that Rafa Benitez's spent half the season leading this team, given that defensive solidity is, or was, his biggest selling point as a manager.

And so, it's very simple. Real Madrid's defensive performance must improve if they are going to remain one of the top teams in the world.

Given the immense wealth and resources at Real Madrid president Florentino Perez's disposal these are the kinds of warnings it should be easy to address. But one issue that makes this tricky is that Real Madrid are banned from registering new players in the next two transfer windows.Even if they weren't, these are the exact kinds of problems Perez has historically been uninterested or unable to fix.

Real Madrid's history of managerial churn, combined with Perez's star-based Galactico approach to team building does not lend itself well to a team whose problems are much more mundane. The temptation, especially after five years of mostly uninterrupted success, is to find the person at fault.

There were no trophies won last season? Fire Carlo Ancelotti and bring in a famous coach with questionable, at best, chances of succeeding in Rafa Benitez. Madrid are struggling under Benitez, fire him and bring in Zinedine Zidane, the very definition of star power, who also is completely untested as a top level manager.

At the same time it often seems Perez's approach to management mirrors that of the fan base he shepherds. Few fan bases in the world focus their ire on a single player the way Madrid does. Gareth Bale is the most recent and prominent case on a long list.

The important thing, though, is that the major point of contention between fans of Real Madrid and the President of Real Madrid is not over whether or not it should all be one person's fault, but simply whose fault it should be.

For fans, getting rid of Bale last summer was the solution. For Perez, it was getting rid of Ancelotti (it's worth noting that during Madrid's struggles this season Bale has been frequently injured and off the field, which has, at least, spared him from enduring as much vitriol this season).

Madrid's success over the last half decade has come in spite of these tendencies. It's come because for three years they had Jose Mourinho who had absolutely no compunction about starting from defensive solidity and building from there. Even if that stance meant marginalizing a Galactico like Kaka.

It came because Ancelotti is uniquely talented at shoehorning many attacking pieces into a mismatched whole, whose defence exceeds the sum of its parts. And it came when Cristiano Ronaldo was more than the elite penalty box poacher he's slowly morphing into and was instead a uniquely gifted goal-scoring winger who unbalanced entire defences.

Ronaldo might be the best pure goalscorer in the world right now, but he no longer unbalances his opposition the way he used to, and if teams don't have to commit two or three of four guys to stop the kind of elegantly tricky runs he used to make, those players are free to stymie (and counterattack) Madrid elsewhere.

It's a natural evolution for Ronaldo, 31, who's already a couple of years past the age when most players begin to decline. But the changes in Ronaldo's game are a harbinger of things to come for Madrid. The team that Real Madrid put on the field three years from now is not going to look like the one they have now.

Ronaldo eventually will either move on to even greener, and slightly less strenuous pastures, or stay at Madrid and have his role reduced. And while Perez may have been preparing for that day by stockpiling top line attacking talent like Gareth Bale, and James Rodriguez, the fact is neither of them, or likely anybody else Madrid might splash giant bags of cash on, will be a true replacement for Ronaldo.

It's certainly possible that a post-Ronaldo Madrid can stay atop world soccer. Madrid could absolutely put together a more balanced attack which doesn't run through him, along with a beefed up midfield and defence, but in order to do that they will need to invest in, or develop, more two-way players. Midfielders that are willing to shield the back four, wingers who track back regularly and energetically, full-backs who aren't simply wingers (or in Marcelo's case, an attacking midfielder) in disguise. With Madrid's money it shouldn't be impossible to do. But then you look at Madrid's transfer record -- and the transfer ban -- and things get complicated.

For a team that has turned Xabi Alonso into Toni Kroos, Mesut Ozil into Gareth Bale, and Angel di Maria into James Rodriguez in the last three years there's nothing to suggest a well-rounded plan lies in Real Madrid's future.

Real Madrid's resources give them a huge advantage over all but the tiniest handful of teams. It's easy to assume that since they have all that money, and they consistently go get whatever players they want, they'll easily transition over the next few years.

But that assumption ignores just how poorly Real Madrid have spent their money in the past, just how much they've focused on big ticket attractive, revenue-driving stars, and ignored the fundamentals of team building.

Now that the end of that era is on the horizon. If Madrid start preparing now, shoring up the defence, diversifying the attack, and generally applying sound principles of team building, then with their resources they'll be a member of the big three for years to come.There's just nothing in their past that suggests that just because they can, they will.