Mark Sanchez is grieving the loss of his former teammate Nick Mangold ... sharing a heartfelt post to social media amid his own legal woes. The former Jets quarterback posted to X hours after news broke that his former center passed away from kidney disease ... writing the world lost a very good football player -- and an even better man. Sanchez believes his pal will end up in the NFL's Hall of Fame eventually ... but, adds his legacy will be so much larger than that -- 'cause he made a lasting