I think that if Hernandez hadn't snorted and smoked his way into an early retirement, he would have easily reached 3,000 hits and won about fifteen consecutive Gold Gloves. That's not an argument for him to get into the Hall though. My argument for him rests on his defense. Nobody played first base like Keith Hernandez. Nobody since him has played it like him either. Mattingly was an outstanding defensive first baseman, but Hernandez was simply nonpareil. He was to first basemen what Ozzie Smith was to shortstops.
Offensively, he was the quintessential #3 hitter. Let's not forget that unlike Mattingly, Hernandez played just about his entire career before home runs started to explode in 1987, and he was a lefthanded hitter without the short porch Mattingly enjoyed. Hernandez was a clutch hitter, too, and I'm not talking about the GWRBI stat in which he usually led the league before it was mercifully shitcanned. I'm talking about the fact that he was ALWAYS the guy you wanted at the plate with runners on in a tight spot -- and the fact that he usually seemed to save a good portion of his 15-18 home runs -- and a hell of a lot of doubles -- for spots like those.
He has nobody but himself to blame for the fact he's not in the Hall. He let his body go to hell and he was just done at an age where guys today seem to be almost just getting started. But if you talk about a healthy Keith Hernandez and a healthy Don Mattingly for 20 years, well, I hardly think the discussion would be "not even close."