Obviously, one can never take anything for granted when it comes to Barca because of their precarious financial situation. There is no guarantee that they'll have sufficient space on their salary bill to sign Rashford next summer - unless he agrees to certain sums and stipulations. However, if Barca do activate their option to buy, it would likely kill off what little chance there is left of the club ever resurrecting the Williams deal for a third time.
When one also considers that Diaz is flying at Bayern, Williams' hopes of finally securing a move to one of Europe's elite next summer actually look quite slim. After all, Arsenal are the only other top team to have been repeatedly linked with Athletic's No.10 and they brought in two wingers during the summer in Eberechi Eze and Noni Madueke.
Is there a chance, then, that Williams may end up regretting rejecting Barca - in much the same what that another proud Basque Martin Zubimendi realised he'd made a mistake staying at Real Sociedad last year? Requesting an exit clause from Barca was unquestionably prudent on Williams' part, while it should not be forgotten that he's effectively living his dream at Athletic, where he gets to play alongside his brother Inaki for a club that has a stronger bond with its people than arguably any other in world football. It's hard to put a price on that kind of privilege.
Nonetheless, the mere fact that Williams twice entertained the idea of moving to Catalunya shows that he is at least interested in testing himself at the very highest level on a regular basis. It also feels telling that while his Athletic buy-out clause was increased when he signed his 10-year contract during the summer, it's still only €90m (£79m/$103m) - which is not an outrageous amount of money for one of the most exciting wingers in world football.
For the time being, of course, Williams' only objective will be getting back on a football field, so that he can then set about getting back to his brilliant best for his beloved Athletic. But he'd definitely be forgiven for looking at what Rashford is doing at Barca right now and thinking that could have easily been him - and maybe even should have been.