It's the same thing that happens to it every year.
Patchwork starting rotation has many, many fewer than average starts that are going six innings pitched or more.
As a result of this, our bullpen throws far too many innings (we are almost always in the worst quarter to third of the league in this metric).
Bullpen gets exhausted by the time June and July roll around. And here we are again, right on schedule.
Because this year's really been no different... and has been exacerbated further by some guys underperforming most of the year, and not being given the ball as much (Pérez, Akin), or having highly specialized roles (Coulombe, a textbook LOOGY, is much harder to get into games in the age of must-face-three-batters-or-have-an-inning-change). This means other guys have pitched so much that their arms might fall off at any second (as in Bautista, Cano, and Baker, who've have thrown a ton of innings due to appearing in almost every close game we have).
We should have been doing it during the last off season, but a couple of consistent, long appearance starters absolutely HAVE to be acquired for next year going forward. We can't keep treating our relievers like this and also have a consistently successful team.