Tbf I never felt Paulinho was a proper workhorse (in term of hard work). We'll need to sign someone if he leaves, indeed.
Paulinho is crap. Awful technique, he's a poor man's Fellaini and never a Barca player.
Willian is a good upgrade on him (a Barca midfielder with pace, whatever next?) but his age is not the profile of player we need to be signing, he's already peaked and hasn't exactly had a great career, in an out of the Chelsea team and no real impact with Brazil.
We always miss out on the right profile of player. Malinko-Savic, Fabinho, Keita, Fred, Jorginho, maybe even Mahrez or Lemar. All players available this summer, while we got dicked about by Griezmann.
Other big teams know what they're doing in the market.