#2 Renato Sanches
If Anthony Martial has failed to live up to his true potential after winning the Golden Ball, Renato Sanches is a player who has straight up buried it. 2016 was an amazing year for Renato Sanches. He shone for Benfica during the first half of the year, was a key part in Portugal's Euro winning squad that summer and then went on to earn a transfer to Bayern Munich in a deal that could have potentially cost them €80 million. It didn't, because that's where it all went wrong.
Renato Sanches struggled for game time at Bayern Munich due to the presence of established midfielders such as Thiago and Vidal. He did go on to win the Golden Boy award later on that year, but it was a downhill slope from there. Even when he did get playing time Sanches failed to reproduce the kind of form he exhibited for Portugal at the Euro. At the end of the season, he failed to score a single goal or grab a single assist, playing in only 25 matches throughout the season. Bayern decided to send him out on loan to Swansea City to gain more first-team experience. It was a disaster. He had a poor season, even by his previous standards and failed to play a single competitive match from January through to the end of the season.
He's since returned to Bayern Munich as new coach Nico Kovac hopes to get him playing at a world-class level again, but it might just be a lost cause.