Longstaff is the one that immediately comes to mind, already mentioned obviously. I'd hope that was just paper nonsense, or maybe some noise from his side. Surely nobody at the club was taking a real look at him?
Matt Ritchie, when he was at Bournemouth. That was also an odd one. We seemed to be linked with a few of their players. Josh King on more than one occasion, and Brooks.
Also Jasper Cillissen. Perhaps a bit harsh as he's a decent keeper, but an enormous downgrade on De Gea at the time.
And the lad that Liverpool signed who is now at Southampton. Minamino(sp?) though that news came out after he signed for Liverpool, I believe.