I see where you are coming from with this, but to me, it is no different than a player signing a PEPSI or DICK'S SPORTING GOODS logo baseball. Signing a HOF logo ball doesn't imply he is in the Hall of Fame and those balls aren't exactly a thing anyways as far as I know. Now making and having him sign a HOF plaque postcard, that is a different sotry. That would be sacrilegious.
Not cool, it's like talking about a perfect game/no-no before it's complete, you jinx the whole thing.
Perhaps if someone were targeting an actual HOFer and they didn't expect him and they were a big fan I would understand but this seems much different than that.
Stupid idea since there are so many reasons a player may not make the HOF. And as others have written, it's disrespectful and presumptuous for a player to sign a HOF ball.
Even getting Mike Trout on a HOF ball is a bad idea since a freak injury could end his career before the requires 10 years of service.
Of course the ball was signed when Hernandez was great, but he now has a 0% chance of making the HOF.
His last three seasons his ERAs have been 4.36, 5.55 and 6.32, he's chronically hurt, was just put back on the Injured List again, he's 33 and this is the last year of his contract. No team will probably sign him for next season and his career numbers are far from spectacular.
I think he'll be like Johan Santana, remembered for having a nice stretch of a few years, then failing to get 5% of the HOF vote after he retires.
As a firm believer in jinxes, in my mind, Hernandez signed these balls years ago, and his career immediately went downhill. He unintentionally derailed his own career by signing these balls. It's his own fault.
You never mention a no-hitter while it's in progress. You don't touch the Stanley Cup or Lombardi Trophy before you've won it. And you don't sign a HoF ball until you get the call.