Here are the potential consequences for both sides at being unable to strengthen their squads for 12 months once the transfer window closes at the end of the month:

No Galactico for Zidane
The news is a huge blow to Real just over a week after they hired French legend Zinedine Zidane as coach. Zidane won’t have the luxury offered to other Madrid bosses of a superstar signing, like he was when signing for the club for a world record fee in 2001, despite reported interest in the likes of Paul Pogba and Robert Lewandowski.

Ronaldo, Bale set to stay
Fortunately for Zidane, he already has one of the biggest and best squads in world football at his disposal in no desperate need of renewal. Indeed, the news could come as just as big a blow to the likes of Manchester United and Paris Saint-Germain, whose hopes of landing Madrid stars Gareth Bale and Cristiano Ronaldo  this summer appear to have ended with Real highly unlikely to sell their best players whilst unable to sign suitable replacements.

Griezmann untouchable at Atletico
News of Atletico’s plans to offer a bumper new deal to top scorer Antoine Griezmann had already circulated in Thursday morning’s papers before the news from FIFA arrived. A new contract would also include a bump in his buyout clause, warding off potential suitors for the Frenchman until after the sanction has been served.

Simeone’s future in the air
Atletico have done remarkably well to replace a host of star players that have left the Vicente Calderon in recent years. It would be much tougher, though, to find someone to replicate the success Diego Simeone has produced in turning the club’s fortunes around in the past four years.
Simeone is contracted to Atletico until 2020, but has been touted as a potential suitor for Manchester United and Chelsea. The idea is for the Argentine to lead Los Rojiblancos into their new stadium in 2017, but the ban may accelerate his desire for a change of scenery, especially if Atletico manage to land La Liga or their first ever Champions League this season.

Advantage Barcelona
Barcelona are the perfect example for their rivals in the capital to follow, having delivered five trophies in 2015 in a year they were banned from registering new players. Barca got ahead of the game in signing the likes of Luis Suarez and Ivan Rakitic in the summer of 2014 before their ban came into force.
That option is open to both Madrid clubs, who have the rest of the January window to add to their squads, but it is much harder to find quality recruits midway through the season.
With the ban minimising their competition in the transfer market and on the field, the coast is clear for Lionel Messi, Suarez, Neymar and company to continue to reign in Spain.