The failure to sign Ronaldinho is probably one of Real Madrid's biggest regrets, as the nimble-footed Brazilian played a massive role in Barcelona's dominance of La Liga in the 2000s. Ronaldinho was one of the greatest players to have ever set foot in Spanish football, and what made it worse for the Madrid faithful was his exceptional performances against Los Blancos time and time again.
One such performance came against their El Clasico rivals at Santiago Bernabéu, where Ronaldinho almost single-handedly brushed aside the men in white, scoring two stunning goals to beat Iker Casillas. "Dinho", as called endearingly by the fans, was one of the very few Barcelona players to have received a standing ovation from the opposition fans at Santiago Bernabéu.
When the Brazilian was available in the transfer window, following his departure from PSG, Real Madrid President Florentino Pérez had a chance to sign the dynamic forward. However, Pérez passed on that opportunity to sign David Beckham instead, as he was believed to be more marketable than Ronaldinho. Although Beckham enjoyed a glorious spell with Los Blancos, Ronaldinho will always go down as a great miss for Los Blancos.
#2 Neymar Jr.
It is no secret that Real Madrid have been vying for Neymar's signature since his days at Santos, but the Brazilian joined bitter rivals Barcelona instead.
Linking up with Messi and Suarez back in the day, the trio formed arguably the most feared attacking cohort in world football. The 29-year old shifted base to Camp Nou in the summer of 2013, and in the 2014-15 season he laid his hands on one of the most coveted trebles in European football - La Liga, Copa Del Rey and Champions League.
Real Madrid tried to sign the Brazilian unsuccessfully, not once, but twice. The first attempt was made during Neymar's time at the Santos youth academy when they wanted to acquire his services for Real's youth academy.
Neymar was just 13 at the time and preferred to hone his skills at his hometown in Santos instead of moving continents to Madrid. Seven years later, Real Madrid tried to sign the 29-year old once again, but after a bidding war with the biggest clubs in world football, Neymar decided to sign on the dotted line for Barcelona.
Neymar's move to Barcelona can arguably be seen as another consequence of Ronaldinho's stint at Camp Nou, as the budding Brazilian superstar wanted to follow in his Brazilian idol's footsteps. The failure to sign Neymar saw Real Madrid snap up Gareth Bale in the 2013 summer transfer window.
#1 Lionel Messi
Yes, you heard that right - Barcelona legend Lionel Messi could have almost signed for Los Blancos, as revealed by his former agent, Horacio Gaggioli, in an interview with ESPN.com. Gaggioli was Messi's agent during his youth days and was given the responsibility by Messi's family to take their son to a city in Spain.
In the interview, he said, "Due to life circumstances, I went to live in Barcelona, and I brought him to Barca for a trial. But I was about to live in Madrid. If that had happened, I would have taken him to Madrid for a trial. That's life; those are the details. Today, Messi could have been a Real Madrid player."
It was also reported in recent years, specifically by Spanish outlet Cadena COPE, that Real Madrid President, Florentino Pérez tried to sign the Barcelona legend on three separate occasions but was reportedly met with a "Thanks, but no". Although Perez has a reputation for pulling off some of the biggest signings in modern football history, the signing of Messi was probably a bridge too far even for the Real Madrid Supremo.