Or Hayden is moving down to 5th choice, which is probably about right tbf. As it stands, if Shelvey or Diame were to get injured, we would only have 1 back up midfielder in Hayden/Merino (depending on which stepped in). That's not enough for comfort.
We had 5 this season with Saivet and Rafa seemed to decide in January he only needed 4 tbf.