Their ace isn't pitching like an ace
As bad as Goldschmidt has been, which I think it is pretty safe to say he's underperformed the most out of every Cardinal this season, the one guy who the Cardinals could not afford to have a "down year" was their big free-agent acquisition, Sonny Gray.
After an incredible start to the season, Gray has fallen off in a major way, and his summer has been defined more by the fly balls that are leaving the ballpark than the elite swing-and-miss Gray has in his arsenal.
While I have a lot of optimism regarding Gray's future outlook with the Cardinals, I completely agree that his performance this year has been disappointing. His home run rate was going to go up this year, we all knew that, but going from truly elite at preventing home runs last year to one of the five worst starters in baseball in regards to HR/FB rate is unacceptable.
What drives me bonkers is how often we've seen Gray look untouchable on the mound for most of his start, but then he'll just randomly leave the ball over the heart of the plate and allow a game-changing home run to occur. Gray currently sits with a 4.07 ERA, and it is truly a mystery how his FIP is still just 3.34. It is a testament to how good Gray has been at striking out batters (30.4 K%) and preventing base runners in general (1.13 WHIP).
Out of all of the things on this list, Gray pitching like a front-line starter down the stretch is actually the thing I could buy into the most. Again, Gray's home run issues are real and they aren't as simple as snapping your fingers to fix, but we've seen Gray be dominant for sustained stretches this season, and I still believe he has that in him when you watch him pitch.
It's hard to bank on that though, and assuming the Cardinals recognize they are out of the race in the near future, I would not be surprised to see Gray's usage go down and try to protect his arm for 2025. It's been a disappointing year for Gray, and it is one of the many reasons the club has struggled this year.