I'd have no problem with Hudson being in either. Him an Buehrle are the only pitchers in MLB with 3,000+ IP from 1999-2015 so they get their own personalized FanGraphs leaderboard to click around on...
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Even with a two season head start, Hudson (479 GS | 3,123 IP) still ended up pitching a lil less than Buehrle (493 GS | 3,283 IP), but Tim was better on a per inning basis with an 83 ERA- | 90 FIP- versus an 87 ERA- | 93 FIP- for Mark.
Add it all up and rWAR favors Hudson (64.2 vs 59.9) while fWAR favors Buehrle (52.3 vs 49.0).
The common denominator holding them back would seem to be they were lifelong peripherals beaters who didn't strike guys out (92 K%+ for Hudson, 78 K%+ for Buehrle) with Hudson getting most of his value from the unsexy combo of ground balls (131 GB%+) and homer avoidance (69 HR9+) while Buehrle never walked anybody (65 BB%+) and fielded his position like a wizard (+87 career DRS, Greinke is second all time at +55).
But yeah, I don't have high expectations. When a guy like Kevin Brown (3,256 IP | 78 ERA- | 78 FIP- | 72.9 rWAR | 76.5 fWAR) who suppressed home runs (58 HR9+) better than anyone in the post-integration era falls off the ballot on his first go round, the electorate clearly isn't paying close enough attention.