Atlético Madrid Football Leaks revealed details of the transaction

Atletico Madrid sold 30 percent of Koke's rights to Quality Football Ireland in 2013 to partially pay off a debt they had with said investment fund.

According to Football Leaks, that 30 percent was worth 3 million euros, meaning that Koke's market value back then was roughly 10m euros.

"The agreement between both parties has the purpose of finishing the previous deal dated back to October 20, 2011 regarding the player Eduardo Salvio," reads the document.

Quality Football Ireland has been related to former Chelsea Director of Football, Peter Kenyon, and some players who have Jorge Mendes as their agent.

Koke was a key player for Atletico Madrid that year, having started 38 matches and in accordance with the Quality Football Ireland agreement, the club had to report "every negotiation regarding the player."

As a result, Quality Football Ireland have the right to ask for 30 percent of any eventual transfer fee for the Spanish midfielder.

In the case of Koke and Atletico signing a contract extension, the fund could either keep that 30 percent holding in the player, and cash in on a future transfer, or ask for the payment of the initial 3m euros , plus a yearly 10 percent top up from 2013 until the signing of this extension, which came in in 2014.

Koke is under contract with Atletico until the summer of 2019.