As reported in The Athletic, medical scans had indicated a potential metatarsal issue which turned out to be the injury the player suffered during United's pre-season tour in the US which has placed the player on the sidelines before the season has begun.
The Frenchman has since gone throughs surgery after being spotted on crutches after leaving pitch against Arsenal.
United knew about the 18-year-old's potential issues, but their executives were determined to proceed with the transfer anyway despite the risk.
This is most likely due to the interest from Real Madrid who were chasing the young star which meant United had to act quick in order to get his signature.
Erik ten Hag’s desperately needed more defensive depth this summer window but the rush to sign Yoro has clearly backfired as the ignorance over Yoro’s metatersal issues has left the side with yet another injured defender.