Yes, there was a change that made fatigued relievers pitch worse:
https://forums.ootpdevelopments.com/...d.php?t=309465
Depending on how many innings you get out of your relievers in the rotation, I assume you frequently have relievers pitching something like 3 games and 4 innings over 5 days. The developers decided relievers coming in with that much fatigue were having too easy a time muddling through, so they were nerfed. With all due respect to your ingenuity, I think yours is exactly the kind of unrealistic roster construction strategy this change undercuts. I don’t think “unrealistic” creativity is a bad thing, but I absolutely see why a game purporting to simulate MLB would benefit from not overly rewarding players for strategies that nobody in MLB has ever considered a good idea.