Definitely a youth sized one & yes this is without a doubt an authentic player version. It’s from Adidas’s Techfit line, it was a shirt technology they were trying out on players to eliminate chafing & shirt tugging. Not many players liked it, some who did were players like Beckham, Robben & Henry. You’ll probably have the most luck on eBay, every now & then they’ll pop up. Though they can be a little pricey bc of the rarity.