This would seem to be a great time to be Sonny Gray. He’s long been a member of baseball’s middle class - at 33, this is his fourth straight year with a salary exceeding $10 million, but he’s never really had that BIG payday. And here is, in the season’s last month, pacing the AL in both ERA (2.92) and FIP (2.82), not including last night’s start. All on the eve of hitting the free agent market at season’s end.

Gray has seemingly answered the single question about himself this season - durability. It’s a natural concern when you stand all of 5’10”, 195. I scouted Gray out of high school and can state unflinchingly that he was not your typical sub-six-foot righty pitching prospect. He has always had lightning-quick arm speed and well above average athleticism. While his frame was slight coming out of high school, everything worked smoothly, his delivery was sound and I would have had no problem drafting him high. But off to Vanderbilt he went, and Oakland took him with the 18th overall pick of the 2011 draft.

That said, he has only pitched enough innings to qualify for the ERA title once since 2019 - at least until last night. While he has kept his employers wanting a bit in the quantity department, the quality on a per inning basis has been there - his has a career ERA- of 84 and FIP- of 86. Proving his durability this season should be enough to warrant a significant investment in this winter’s free agent sweepstakes, right? Not so fast.

Take one look at Gray’s basic 2023 stat line and what jumps out at you? That absurdly low total of six home runs allowed. In this day and age, six homers in 157 innings just seems too good to be true. And it is.

Gray has done a nice job of limiting authority in the air this season - but not nearly an all-time great one. His 90.0 mph average fly ball exit speed, while almost a full standard deviation lower than league average, is actually the highest mark he has allowed since 2017. His Adjusted Fly Ball Contact Score of 84 is solid, but way higher than his unadjusted, actual mark of 60. The other Gray in the AL, the Rangers’ Jon, actually has done better. He’s also been fortunate on liners (86 Unadjusted vs. 101 Adjusted Contact Score), grounders (94 vs. 102) and overall (79 vs. 96).

His 93.6 mph average line drive exit speed is his worst since 2018 and his 86.9 mph average ground ball and 88.7 mph overall average exit speed are both his worst marks since 2016. While none of these figures are “bad”, they’re not exactly what you’d expect from a pitcher whose mainstream stats seem to be leveling up this season.

Gray’s 68 ERA- and 66 FIP- are almost exactly equal, but my batted ball-based proxy, “Tru”ERA-, is much higher at 88. FIP is giving him full credit for not allowing homers and running a strong grounder rate, but the truth is, he’s allowing almost league average range contact quality.

Breaking things down to a pitch-specific level, more concerns emerge. I annually issue letter grades to each offering thrown by starting pitchers accumulating 135 or more innings, based on their bat-missing and contact management performance relative to the league.

Typically, Gray has succeeded qualitatively by combining a plus sinker with a plus slider. The former got an “A” in 2019, an “A+” in 2020 and a “B+” in 2021. The latter, a “B+” in 2019 and an “A” in 2021 sandwiched around an odd “C” grade in the pandemic-shortened 2020 season. His other two longstanding primary offerings, his curve and four-seamer, have consistently been average to slightly below average pitches. (He has to his credit added a cutter to the mix this season, and it gets an interim “B+ grade.)

In 2023, besides that new cutter, he has only one above average pitch - the slider, which has been a brilliant “A+” offering this season, with a sterling 23.6% pitch-specific whiff rate and a strong 77 Adjusted Contact Score. What’s not to like about that?

Well, when your only out pitch is a slider, you’re living on the precipice. Ask Patrick Corbin and Shane Bieber all about that. It’s not good business to be totally reliant on a pitch that can suddenly ebb in effectiveness at any time.

His fastballs both continue to be average at best, and the trend lines aren’t positive. Gray has logged 5.8% and 6.5% swing-and-miss rates on his four-seamer and sinker this season, earning “C+” and “B” grades to date. That matches or falls short of his career worst grades for those pitches going back to 2019.

So buyer beware when considering going long on Gray this offseason. Yes, the newfound durability is encouraging, but there are no guarantees on that front moving forward. And the intermediate-term track record of slider-first/slider-only starting pitchers typically isn’t very good. As always, pitching will be in short supply in this winter’s free agent market, and Gray may be a very expensive mistake waiting to happen.