Of course it's not a matter of rotating in the last month, who asked for that?
It was a tough schedule from december to march, and Pedri for instance played almost every single minute there. If he was the best option, he should've been rotated out for a few more games in that time period, so that he was more fresh when it mattered more in the last couple of months. Griezmann was another one who always played when fit, and who seemed fatigued.
Rotating is done throughout the season in order to always have a lot of fresh AND match fit players available.
Problem was that Koeman needed far too long to find a decent first 11 and system. Hopefully things are clearer now for him.
Hopefully, but I'm not sure. It's 4-3-3 again in preseason, and I think Koeman will play like that until he plays a disappointing game, then he'll change if he is not under too strict of an ultimatum from Laporta...
Last season, he switched thrice just in the last months, always after defeats.