The Brazilian—considered by some to be still one of the best midfielders on the planet—has since become a bench player who rarely gets called up by Jose Mourinho.
This article will look at what Kaka's role can still be with the club and how he has been completely misused by his Portuguese manager—even to the point of negatively impacting other players on the team.
Many see Kaka's time at Real Madrid as a failure, and while that is a completely fair argument, it would be unfair to blame the player for this.
First of all, it is not entirely conclusive that Kaka has been a failure.
His numbers have not been worthy of his transfer fee: Twenty goals in 71 appearances is not bad at all for an attacking midfielder, but it is for a former Ballon d'Or winner who recently turned 30 and cost more than any midfielder in history.
However, Galacticos are never bought only for what they provide to the team. Shirt sales, global expansion of fans and general popularity are all major reasons these superstars are brought to the Bernabeu.
Kaka has not been a wild success, but to say he has been a bust would be a bit unfair. He has bought a lot of revenue to the club and helped expand the fan base.
Plus, when he has played, the South American has proven valuable and useful. It's just getting on the pitch that has been a major problem—which leads me to my next point.
Why doesn't Mourinho use Kaka?
Who is more to blame for Kaka's 'failure' at Real Madrid?
Before we can say that Kaka is still good enough to play for Madrid or still deserves to play, we have to look at more than just the stats or number of appearances to date.
We have to look at his growth over time and the current level of form and fitness.
In his first season, Kaka was a general success. He helped Los Merengues win more points than any other club ever had in Spain. Unfortunately, Pep Guardiola's Barcelona bested that mark in the same year.
The 2010-2011 season saw Kaka miss over eight months to injury, and he never really got back near top form until the next campaign.
Since returning from injury, the Brazilian has gotten consistently stronger and better.
The failure of Kaka...or Mourinho?
It was understandable that Mourinho wanted to take his time with Kaka last season, since his injury was very serious and the team was doing just fine without him.
This term, however, has been a different story. The poor forms of Mesut Ozil and Angel di Maria, specifically, provide plenty of opportunities for Kaka to play and establish himself as a first-team regular again.
And really, the current situation is only a continuation of last spring. Since coming back from a lengthy injury Di Maria has not really been the same player who almost broke La Liga's assist record in a single half.
While the Argentinian—as well as Ozil and even new signing Luka Modric, to a lesser extent—have been in poor form, Kaka has been pretty sensational for most of the time he has been on the pitch, going back to last winter.
Yet, despite the 30-year-old's great health, Di Maria's challenges in regaining his form and despite the continued struggles of the Madrid defense this season, Jose Mourinho continues to misuse Kaka.
The Portuguese coach seems content with letting Madrid's former record signing waste away on the bench—a player who could still start for almost any club in the world.
Mourinho also failing Ozil
Sitting on the bench watching his club and fellow teammates obviously hurts Kaka, especially at the age of 30.
The longer he fails to get consistent action, the more fans are robbed of watching one of the last decade's elite players regain his old form.
But Kaka is not the only player suffering from his absence on the pitch. Oddly enough, it is the man he most commonly comes on for who is also being held back under Mourinho—Mesut Ozil.
On a good day, the Ozil is one of the most elite players on the planet. His vision, passing range and accuracy are almost unrivaled.
Unfortunately, the German international struggles with consistency, especially in big games. He is currently in the middle of the worst slump of his career. As we enter December, Ozil is having his worst season since coming to La Liga and is seemingly falling out of favor with Mourinho.
When the Portuguese coach gets his first-half tactics or squad selection wrong, it is usually Ozil he blames and takes out of the game.
The 24-year-old is certainly struggling, but the reason for that goes beyond an extended dip in form.
Ozil not fitting in
The problem for Ozil is that he does not quite fit into Jose Mourinho's defensive, width-reliant counter-attacking game—or perhaps it is more accurate to say that his support does not fully suit him.
In the current set-up, Ozil is simply being held back.
Is Ozil too smart for this Real Madrid team?
He is partnered on both flanks by incredibly gifted wingers, but both Cristiano Ronaldo and Angel di Maria lack the technical or creative quality of the German and rely more on their physical strengths.
Both players are very wasteful with the ball and—in terms of aiding into the attack with a more involved and consistent role—are far too streaky.
Most importantly this season, no one in Madrid's attacking midfield is disciplined, patient or creative enough to break down a stout defense like Ozil.
Without that help, Ozil is left directing play from the middle, only to have his wingers either waste a shot or take the ball out wide just to send a low-percentage attempt into the box.
Kaka's 'Ozil Effect'
One player who works very well with the great German midfielder is Kaka.
After Madrid's last group stage match against Borussia Dortmund, I made the point that Ozil may be better suited for a team like Dortmund or even Barcelona—a team with more true midfielders in attack than a pair of false wingers with less football intelligence from that area.
Many criticized me for even suggesting that Ozil is not fitting in, citing the great assist numbers the Madrid No. 10 had last term and the overall stellar season he had.
What many fail to realize is that the greatest stretch of Ozil's campaign did not come with the current Madrid team.
The German was at his very best with another creative midfield alongside, most often Kaka.
It was the Brazilian's mastery of the ball and ability to control the midfield while slowly and deliberately breaking teams down that saw Ozil gain more freedom.
He would often slide out wide like he does for Germany or stay more centrally while still being awarded tons of space to roam.
Having two world-class midfielders gives so much more tactical variety to Madrid beyond a counter-attack or trying to score within a minute of reaching the final third.
Now Ozil has to fully take on the role of playmaker by himself with neither midfield partner having much to add and comparatively lacking in football intelligence.
Should Kaka start more right now?
Unfortunately, instead of Mourinho choosing to partner Kaka beside Ozil in midfield, he uses him as the direct replacement, still limiting the team in a similar fashion.
It seems more fans are wising up to the fact that the attacking midfield trio has many limitations, especially against top teams or those with great midfields.
Mourinho remains characteristically stubborn in his tactics and squad selection, though—a problem that greatly cost his team in the second half last season.
This weekend's Madrid Derby would be the perfect opportunity to try using Kaka with, rather than instead of, Ozil. But it likely won't happen.
The German just played another match mid-week, and if the Brazilian plays it would likely only be in his place.
Conclusion: justice unlikely
Long-term, if Madrid want to keep Mesut Ozil happy and maximize his talent, they need to start building around him and not the quick, wide counter-attack of Mourinho.
One major step toward getting the most from him would be to play the incredible Kaka alongside him, perhaps even pushing the German into the wide role he performs so well with Germany.
The team is so talented that they will be fine most of the time and will still score loads of goals with Ozil having a pretty successful season.
However, those problems will continue to show up all season, and the poor connection Ozil has with Di Maria will probably not become a serious issue until big matches later in the season.