The downside is that Bieber's stats this year haven't been nearly as good as they've been in years past. His 3.77 ERA isn't bad, but it's the highest he's posted since his rookie year in 2018 when he had a 4.55 ERA.
While I typically don't put too much stock into FIP, his mark this year is not very good. The main concern I have however is his injury history. He's on the IL with elbow inflammation right now, and he was limited to 16 starts in 2021 due to shoulder troubles, so that's something the Cardinals are going to have to keep an eye on.