Mbappe, Alli and Leroy Sane among most valuable U21s: CIES Dec 05, 2017 Kylian Mbappe is now Europe’s most valuable young player as the 18-year-old’s form begins to match up to his £166million planned purchase fee for Paris Saint-Germain. Share 0 Share on Facebook Tweet Tweet on Twitter +1 +1 on Google Plus