Research group CIES Football Observatory have set Dani Ceballos' value if Arsenal were to take him from Real Madrid on a permanent deal.
To complete the loan signing of the Spaniard this summer, the Gunners had to part with £15million and agree to not having an option to buy the midfielder.
Ceballos stole the show on his debut with an impressive performance against Burnley but his displays have not quite been up to the same level since.
According to CIES Football Observatory, the 23-year-old currently stands at the second-most expensive loan player in Europe's top-five leagues at £56million.
Since his move to Arsenal, despite not living up to his initial expectations, Ceballos has been used favourably by Unai Emery.
The Arsenal boss has tinkered with his side often this season, but there has always seemed to be a place for his fellow countryman. He has played as a deeper lying midfielder, just behind the strikers and even out wide.
Although he has been tidy with the ball at his feet in all these roles, the Spaniard as struggled to have a real impact on games. In a team that has become more dangerous on the counter-attack than when building their own attacks, his attributes haven't shone through. Not the quickest, he often has to cut back and wait for support which kills Arsenal's counters.
Pulling his hamstring against Vitoria in the Europa League, Ceballos will have the international break to recover but his performances must improve if Arsenal are to make his stay in north London permanent.
Also on CIES Football Observatory's list was Arsenal's William Saliba who is on loan at Saint-Etienne. Yet to be on the losing side in Ligue 1 this season, signing the 18-year-old in the summer is looking more promising by the week.
The Gunners secured Saliba's signature for £27million in the summer and off that back of his performances this season, that figure has risen. The Frenchman is now valued at £30.1million and is the ninth most expensive loan player in Europe.
A brighter prospect than Ceballos has been, the young centre-back will be a welcome addition at the Emirates next summer.
