We need to rotate in these games. No better games to do it other than Copa.
There is a difference between:
1. playing 11 starters all the time
2. rotate 2 players
3. rotate 4 players
4. rotate 6 players
5. even worse, put 4-5 new signings with not too much chemistry and automatism in the same time in lineup.
After all, new players need to gel with starters, not with 5 other new signings who will be squad players.
Arthur needs to click with Rakitic and Busi.
Not with Roberto and Rafinha, for example.
Malcom needs to click with 2 out of Messi-Suarez-Dembele in attack.
Lenglet needs to click with Pique or Umtiti. Not with Vermaelen, for example.
Ok, I went into extremes, but you get the point.
Today it would be fine to play 1-2-3 squad players, but not suddenly play ALL new signings, like Arthur, Vidal, Malcom, Lenglet together on a field.