The Sonny Gray signing is both a very good thing and a concerning thing

Gray will improve the rotation quite a bit while on a sensible contract, but he shouldn't be the final addition

It’s not even December yet, and the Cardinals on Monday added a third new arm to the 2024 rotation. After landing Lance Lynn and Kyle Gibson mere days ago, the Cards struck near the top of the market in adding Sonny Gray on a three-year, $75 million pact. 

First, the good. Gray moves the needle for a rotation that was infamously lacking in 2023, and they fetched one of the best starters on the domestic free-agent market without committing to him beyond his age-36 season. I knew Gray might be eye-balling retirement before he reached his late thirties, but I still expected him to sign a four-year deal. From the organizational standpoint, three years is a win. 

As for his outlook, it’s a promising one. I’ll quote myself at length from this October piece in which I stated my preference for Gray over Aaron Nola, who wound up returning to the Phillies. On Gray: 

Gray, who turns 34 next month, arrested what had been a concerning decline in K% (strikeouts as a percentage of batters faced) prior to this season, and it’s mostly because of increased use and improved command of his sweeper, which is the whiff pitch du jour in MLB. As well, the addition of a cutter to Gray’s arsenal and increased use of his changeup have given him a full and baffling six-pitch arsenal with the proper array of spin profiles and pairings.  

When pondering whether a pitcher like Gray has successfully adapted to advancing age, you want to see something like arsenal changes and progress at fundamental indicators underpinning surface-level outcomes like ERA – things like K%, swinging-strike rate, and chase rate.

In Gray’s case, yes, we have repertoire adjustments as noted above, and we also have some promising statistical trends. As mentioned, he’s halted a slide in K% that had been in place since 2019, and his K% is up modestly over 2022 levels (24.3% this year versus 24.0% last year). More promising is that Gray this season put up a swinging-strike rate of 12.5%. That’s up from 9.6% last season and is his highest such figure since 2017. His chase rate, or how often he gets hitters to swing at pitches outside the strike zone, is also back to its highest point since 2017. These are all good things when it comes to Gray’s near- to mid-term outlook. 

No, Gray is not a hard thrower, but his fastball may play up a bit because he gets above-average extension off the mound and good spin. The trendline is noteworthy, since his hard stuff has increased in velocity relative to last season. As well, that K% of 24.3 is solidly above the MLB average for starters of 22.1% and far above the Cardinal rotation’s mark of 17.4% (which is higher than only that of the Rockies’ starting pitchers in 2023). 

The Twins plainly coached up Gray, especially with the sweeper, and given how far ahead they are of the Cardinals in terms of pitching infrastructure, you worry about his capacity to port those gains over to our side. The great Joe Sheehan raised this point to me over email, and I do have concerns about that. For now, I’ll assume that’s been taken into account and that Gray and Dusty Blake are confident on this front. It’s something worth monitoring, though. Overall, I’m very bullish on this addition especially at three years. However, that same number – three – raises other, grimmer matters.