20 1st team players is fine as long as they stay fit, which is why he'll trim the odd injury prone player and a few of the oldies.
I'm not including players like Carson, technically Khusanov could come into it too, players it's easier to leave at home. Academy players come into that too.
Barcelona had 19 players over 1000mins this season, 8 players over 3000mins.
Real Madrid had 19 players over 1000mins this season, 9 players over 3000mins.
Arsenal had 20 players over 1000mins this season, 9 players over 3000mins.
Liverpool had 18 players over 1000mins this season, 10 players over 3000mins.
PSG had 19 players over 1000mins this season, 10 players over 3000mins. Shorter league season.
Bayern had 19 players over 1000mins this season, 5 players over 3000mins. Shorter league season.
Leverkusen had 18 players over 1000mins this season, 8 players over 3000mins. Shorter league season.
Inter had 19 players over 1000mins this season, 7 players over 3000mins.
City had 21 players over 1000mins this season, 7 players over 3000mins.
So Pep is right on the squad size, it needs trimming before bringing more quality in. 18-20 solid reliable players. If the injury prone stick around then they can't be counted in that 18-20 and have to be content with being left aside to protect them.
The issue is also the 11 that played the most minutes this season:
--------------Ederson
Lewis---Dias---Akanji---Gvardiol
-------Gundogan---Kovacic
Bernardo-----Foden-----Savinho
-------------Haaland
I've put Bernardo and Foden that way around because they've probably played like that more often than not.
I think if we'd have seen that pre-season, Stones, Walker, Rodri, De Bruyne and potentially Grealish/Doku not in the 11 with the most minutes, we'd have all said we're not winning the title. Then add in the players we would have expected like Foden, having absolutely shockers and it just compiles the misery.