No man is anything close to being age proof, I'm knowledible about MLB. You're pretty much toast beyond age 35+, get your big contract when you are in a position of power guys because nobody wants to sign your (__#__) until you're 40. Very few guys are worth a crap after age 35.
There are of course some exceptions, most oftenly found on the mound or as DH. Starting pitcher David Wells is a great example, that fat fuck was like the John Daly of baseball, pitched effectivelly ,until he was like, 44. He had the talent to be an all time great but didn't care about that
Other guys like a Mo Rivera keep themselves in tip top shape, pitch just 60 innings a year and manage to be revered as the bestest thing since ice cream. Fat fucks like Wells and Colon go on forever
The market for sluggers has leveled out at about 25 M, you might get like 76 M over 2 years, but not 10 years and insane money well past age 35
The only real sport I can think of where a journeyman n pro can still play competively at age 50 or so is Jai alai
All time greats like Chemela can play at the highest levels at age 50
There is/was a paid pro player in Florida that was actively playing professionally at age 55, just because he needed a job.
Rastock or close to that spelling