I suspect they mean the ‘98-born player Upamecano’.98?!
Surely that's a typo!? That's crazy! Wow. He must be the oldest player ever!
Wait wait wait... I just googled and came across several pages hinting Upancomer is much younger than 98... Curiouser and curiouser...
It is very common for young players to be addressed by their year of birth. ‘The 2000 class’ or ‘best from the 1999 group’ etc.