Chelsea wildly overpaid for former Athletic Bilbao goalkeeper Kepa Arrizabalaga, it has been claimed.

The CIES Football Observatory, which analyses football data, suggests Kepa's £71.6m move was a clear £40.1m more than the keeper is worth, so making him the most over-inflated transfer of the summer.

It's also claimed Chelsea undersold Thibaut Courtois to Real Madrid.

Indeed, Chelsea top the list of English clubs who missed out on transfer fees, when they let Courtois go for £20.8m less than his worth.

The changes are worked out by comparing the actual price paid to the CIES Football Observatory's fair price, which the research group says is the "average between the estimated cost for the most likely buyer before the transfer and the current transfer value".