Hernandez featured for Spain against Scotland last Tuesday and will face McGregor against when Valencia take on Rangers in the Champions League on Tuesday.
“He made some amazing saves, it was a fantastic performance,” Hernandez told BBC Scotland.
“Certainly had it not been for him we would have scored a few more goals on Tuesday.
“But obviously he was one of a few Rangers players playing for Scotland and who have been playing at that level and at European level for some time, so it’s going to be a very difficult match.
“It could be pretty similar to the game between Scotland and Spain, in the sense that they’ll be more physical and will battle hard, while we may have more possession.
“But, in any case, it’ll be interesting to come up against these players again.”