Real Madrid have inserted a mammoth buyout clause worth a staggering €500m (£437.7m, $573.2m) into Dani Ceballos' contract after beating fierce rivals Barcelona to the signing of the young Real Betis star, reports in Spain suggest.

According to AS, the reigning Spanish and European champions are eager to eliminate the risk of the highly-rated 20-year-old being lured away in future by any rival – including fellow suitors Barcelona – as they hope to see him develop into one of the world's elite midfielders.

It is also suggested that they wanted to reiterate to the Spain Under-21 star that he is a big part of their future plans, with competition for places under Zinedine Zidane likely to prove particularly fierce early on.

Ceballos signed a six-year deal with Real on Friday (14 July) and will be officially unveiled at the Santiago Bernabeu next week before joining up with his new teammates on their pre-season tour of the US.

Los Blancos are said to have paid approximately €17m for his signature, a fee which stands at €2m over his previous €15m release clause.

The former Sevilla youngster featured 105 times for Betis after making his first-team debut in 2014 and further embellished his growing reputation as one of the most sought-after young players in Europe by spearheading Spain's run to the final of the recent Under-21 European Championship in Poland. He was named as the player of the tournament despite starting two of La Rojita's five matches as a substitute.

Former Premier League target Ceballos is the second player to be signed by Real so far this summer after French centre-back Theo Hernandez, who joined from Atletico Madrid. Mariano Diaz, Pepe, Fabio Coentrao, Diego Llorente and Burgui have all left the club, while James Rodriguez was dispatched to Bayern Munich last week on a two-year loan deal.

Ceballos' contract is not the only one currently making headlines in Spain, with Barcelona's agreement with Benfica for the transfer of right-back Nelson Semedo said to contain something of a unique clause.

As revealed in a post-transfer document released by Benfica and cited by Sport, the Catalan giants must pay their Portuguese counterparts an additional €5m for every 50 official matches played by the Portuguese international until he signs his first contract extension.

Semedo's initial deal with Barcelona runs until 2022 with the option of a further 12 months, meaning that an initial €30m transfer is likely to be worth far more over the coming years.