HoF candidacies are in large part an accumulation game. Jacob deGrom is the per-inning amongst SPs. Some pitcher who has a brilliant but short career - maybe that's deGrom, or maybe he goes R. Johnson post-age 32 on us - is going to test HoF benchmarks https://www.thescore.com/news/2157833 

Among the post-WWII cohort, there is an argument that Koufax has already done this and he's interesting comp. He pitched 12 years, deGrom is in 8th. If deGrom wins a CYN this year, their top-four year peaks will be nearly identical (by ERA+) and deGrom has the better career ERA+

If a pitcher reaches 3,000 IPs, they have very good HoF chances. Of course, those are increasingly the rarest of outliers. It's one reason there have been only two SPs born in the last 50 years to reach the HoF.

I think there's an argument to be made that if deGrom did not pitch another season he's a HoFer. Among SPs to toss at least 1,000 innings, he's the top WAR/inning arm. With a strong 2021, he's a modern-day Koufax, basically. But ...

while the HoF voter is evolving, deGrom only has (looks at his Mets teammates) 72 wins and 1,198 innings. Most voters, I think, will want to see something come close to 2,000 innings and the likely production that comes with that. I could be wrong about that ...

But if anyone is going to break the HoF standards, and help get more modern SP representation in Hall, it might take something like deGrom's 2017-2021 run with a 1,600-1,800 IP resume of work